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Sample records for 14-fr peel-away sheath

  1. The Hickman peel-away sheath: alternative for pediatric percutaneous nephrolithotomy.

    PubMed

    Helal, M; Black, T; Lockhart, J; Figueroa, T E

    1997-06-01

    Percutaneous nephrolithotomy presents a therapeutic challenge in children because of the disproportion between the sizes of the instruments and the kidneys. A technique for pediatric nephrolithotomy used on a 2-year-old female child is presented. The patient was born prematurely and developed kidney stones as a complication of furosemide therapy. She failed medical management with hydrochlorothiazide, and the stone did not disintegrate following extracorporeal shockwave lithotripsy (ESWL). A Chiba needle was used to access the renal collecting system percutaneously. Using a guidewire, sequential dilatation was performed to 16F. A 15F Hickman catheter introduction kit was then used, and the sheath was partially peeled away. A 10F pediatric cystoscope and grasper were inserted through the sheath to remove the stones. A 12F catheter was then placed through the sheath; the sheath was peeled away, and the catheter was left indwelling for 48 hours. No complications ensued. A postoperative nephrostogram showed free drainage and absence of residual stones. Utilization of the Hickman peel-away sheath constitutes an excellent alternative nephrolithotomy technique for children with stones unresponsive to more conservative treatment.

  2. Placement of large suprapubic tube using peel-away introducer.

    PubMed

    Chiou, R K; Morton, J J; Engelsgjerd, J S; Mays, S

    1995-04-01

    We describe a new method for placing a large suprapubic tube and report our experience with 56 patients. This method uses a specially designed fascial dilator and peel-away introducer to place an 18F Foley catheter suprapubically. In our experience the method is simple and effective for the exchange of a small suprapubic tube to an 18F Foley catheter, and for primary placement of a large suprapubic tube. It is easily performed at the bedside or during a minor procedure with the patient under local anesthesia. PMID:7869492

  3. Percutaneous placement of a suprapubic tube with peel away sheath introducer.

    PubMed

    O'Brien, W M

    1991-05-01

    A new technique for percutaneous placement of a suprapubic tube has been developed, which allows controlled entry into the bladder over a guide wire to avoid the potential hazards of blind trocar cystotomy. A Foley style catheter can be placed, which is less likely to become dislodged than other types of percutaneous suprapubic catheters currently available. PMID:2016781

  4. APPARATUS FOR SHEATHING RODS

    DOEpatents

    Ford, W.K.; Wyatt, M.; Plail, S.

    1961-08-01

    An arrangement is described for sealing a solid body of nuclear fuel, such as a uranium metal rod, into a closelyfitting thin metallic sheath with an internal atmosphere of inert gas. The sheathing process consists of subjecting the sheath, loaded with the nuclear fuel body, to the sequential operations of evacuation, gas-filling, drawing (to entrap inert gas and secure close contact between sheath and body), and sealing. (AEC)

  5. Communication through plasma sheaths

    SciTech Connect

    Korotkevich, A. O.; Newell, A. C.; Zakharov, V. E.

    2007-10-15

    We wish to transmit messages to and from a hypersonic vehicle around which a plasma sheath has formed. For long distance transmission, the signal carrying these messages must be necessarily low frequency, typically 2 GHz, to which the plasma sheath is opaque. The idea is to use the plasma properties to make the plasma sheath appear transparent.

  6. Return of the sheath.

    PubMed

    Felstein, I

    1980-10-01

    The history of the condom is reviewed with attention directed to the medical perspective that the return of the sheath to use is hopeful in terms of venereal disease control improvements. By 1950, condom manufacturers could claim that 1/2 of all the married couples using contraception included the sheath as a major or ancillary method in both the United States and the British Isles. The introduction of the oral contraceptive led to the sheath losing a large measure of its once universal popularity. Simultaneously there was a marked increase in venereal infections with a dramatic rise in gonorrhea and non-specific urethritis. Venereologists have been disturbed by the decline of sheath usage. The manufacturers of the sheath did not accept the reduction in sales. Taking advantage of the changed attitudes to sexuality and sex aids, manufacturers began to make colored sheaths and to vary textures in order to raise or lower sensitivity, increase or decrease friction, and add or diminish lubrication. Shapes have also been varied, and several attachments to the sheath have included clitoral stimulators and vulval stretchers. Improved marketing has seen retailing of condoms in open areas. PMID:6903257

  7. Glancing angle RF sheaths

    NASA Astrophysics Data System (ADS)

    D'Ippolito, D. A.; Myra, J. R.

    2013-10-01

    RF sheaths occur in tokamaks when ICRF waves encounter conducting boundaries. The sheath plays an important role in determining the efficiency of ICRF heating, the impurity influxes from the edge plasma, and the plasma-facing component damage. An important parameter in sheath theory is the angle θ between the equilibrium B field and the wall. Recent work with 1D and 2D sheath models has shown that the rapid variation of θ around a typical limiter can lead to enhanced sheath potentials and localized power deposition (hot spots) when the B field is near glancing incidence. The physics model used to obtain these results does not include some glancing-angle effects, e.g. possible modification of the angular dependence of the Child-Langmuir law and the role of the magnetic pre-sheath. Here, we report on calculations which explore these effects, with the goal of improving the fidelity of the rf sheath BC used in analytical and numerical calculations. Work supported by US DOE grants DE-FC02-05ER54823 and DE-FG02-97ER54392.

  8. Transient overvoltages on cable sheaths

    NASA Astrophysics Data System (ADS)

    Dabringhaus, H. G.

    1983-08-01

    Transient overvoltage on the sheaths of high voltage cables with single point sheath earthing or cross bonding of the cable sheaths involve danger for the cable and the joints. The investigations of transient overvoltages in the case of a switching operation on a 110 kV single core oil filled cable with single sided sheath earthing are reported. A comparison between measured transient voltage variations and those calculated with the help of a traveling wave analyzer program shows very good agreement. The investigations showed that with single point sheath earthing, the unearthed sheath end ought to be protected against overvoltages.

  9. Sheath energy transmission in a collisional plasma with collisionless sheath

    SciTech Connect

    Tang, Xian-Zhu Guo, Zehua

    2015-10-15

    Sheath energy transmission governs the plasma energy exhaust onto a material surface. The ion channel is dominated by convection, but the electron channel has a significant thermal conduction component, which is dominated by the Knudsen layer effect in the presence of an absorbing wall. First-principle kinetic simulations reveal a robustly supersonic sheath entry flow. The ion sheath energy transmission and the sheath potential are accurately predicted by a sheath model of truncated bi-Maxwellian electron distribution. The electron energy transmission is further enhanced by a parallel heat flux of the perpendicular degrees of freedom.

  10. 21 CFR 884.5320 - Glans sheath.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... sheath. (a) Identification. A glans sheath device is a sheath which covers only the glans penis or part... the entire shaft of the penis. It is indicated only for the prevention of pregnancy and not for...

  11. 21 CFR 884.5320 - Glans sheath.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... sheath. (a) Identification. A glans sheath device is a sheath which covers only the glans penis or part... the entire shaft of the penis. It is indicated only for the prevention of pregnancy and not for...

  12. Challenging diagnosis of peripillous sheaths.

    PubMed

    Gnarra, Maria; Saraceni, Pierluigi; Rossi, Alfredo; Murabit, Amera; Caradonna, Emanuela; Fania, Luca; Feliciani, Claudio

    2014-01-01

    Peripillous sheaths, or hair casts, are asymptomatic, white, cylindrical concretions that encircle the hair without adhering to it. They are infrequently documented in the literature, are often misdiagnosed, and generate avoidable apprehension and expense for parents and caregivers. Dermoscopy is the standard for a rapid, noninvasive, cost-effective diagnosis. We describe a case of peripillous sheaths presenting in a boy. PMID:24846654

  13. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, John R.

    1987-12-01

    a method for manufacturing a magnet cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible sheath, with the trim coil pattern precisely positioned thereon, is accurately positioned at a precise location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator.

  14. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, J.R.

    1987-05-15

    A method for manufacturing a magnetic cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible substrate sheath, with the trim coil pattern precisely location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator. 1 fig.

  15. Dust in the magnetized sheath

    SciTech Connect

    Pandey, B. P.; Samarian, A.; Vladimirov, S. V.

    2007-09-15

    In the present work the structure of the magnetized sheath is investigated in the multifluid framework. The ambient magnetic field is assumed parallel to the wall and the effect of the plasma magnetization, plasma ionization, and plasma-neutral collisions on the sheath is examined. It is shown that the width of the non-neutral boundary layer is dependent on the collision frequencies as well as on the plasma magnetization. The size of the sheath layer can decrease with the increase in magnetic field. The increase in the ion-neutral collision can also adversely affect the sheath size. The equilibrium and levitation of the dust particles in a collisional magnetized sheath are shown to depend on the collision frequencies and on the magnetization. Further, the increase in the collision or magnetization invariably leads to the presence of the positively charged grains near the plasma wall suggesting that the grain levitation inside the charged layer is implicitly dependent on the plasma parameters in a nontrivial way.

  16. Cascaded target normal sheath acceleration

    SciTech Connect

    Wang, W. P.; Shen, B. F.; Zhang, X. M.; Wang, X. F.; Xu, J. C.; Zhao, X. Y.; Yu, Y. H.; Yi, L. Q.; Shi, Y.; Zhang, L. G.; Xu, T. J.; Xu, Z. Z.

    2013-11-15

    A cascaded target normal sheath acceleration (TNSA) scheme is proposed to simultaneously increase energy and improve energy spread of a laser-produced mono-energetic proton beam. An optimum condition that uses the maximum sheath field to accelerate the center of the proton beam is theoretically found and verified by two-dimensional particle-in-cell simulations. An initial 10 MeV proton beam is accelerated to 21 MeV with energy spread decreased from 5% to 2% under the optimum condition during the process of the cascaded TNSA. The scheme opens a way to scale proton energy lineally with laser energy.

  17. Malignant Peripheral Nerve Sheath Tumor.

    PubMed

    James, Aaron W; Shurell, Elizabeth; Singh, Arun; Dry, Sarah M; Eilber, Fritz C

    2016-10-01

    Malignant peripheral nerve sheath tumor (MPNST) is the sixth most common type of soft tissue sarcoma. Most MPNSTs arise in association with a peripheral nerve or preexisting neurofibroma. Neurofibromatosis type is the most important risk factor for MPNST. Tumor size and fludeoxyglucose F 18 avidity are among the most helpful parameters to distinguish MPNST from a benign peripheral nerve sheath tumor. The histopathologic diagnosis is predominantly a diagnosis of light microscopy. Immunohistochemical stains are most helpful to distinguish high-grade MPNST from its histologic mimics. Current surgical management of high-grade MPNST is similar to that of other high-grade soft tissue sarcomas. PMID:27591499

  18. Plasma sheath criterion in thermal electronegative plasmas

    SciTech Connect

    Ghomi, Hamid; Khoramabadi, Mansour; Ghorannevis, Mahmod; Shukla, Padma Kant

    2010-09-15

    The sheath formation criterion in electronegative plasma is examined. By using a multifluid model, it is shown that in a collisional sheath there will be upper as well as lower limits for the sheath velocity criterion. However, the parameters of the negative ions only affect the lower limit.

  19. Water in the formation of biogenic minerals: peeling away the hydration layers.

    PubMed

    Dorvee, Jason R; Veis, Arthur

    2013-08-01

    Minerals of biogenic origin form and crystallize from aqueous environments at ambient temperatures and pressures. The in vivo environment either intracellular or intercellular, contains many components that modulate both the activity of the ions which associate to form the mineral, as well as the activity and structure of the crowded water. Most of the studies about the mechanism of mineralization, that is, the detailed pathways by which the mineral ions proceed from solution to crystal state, have been carried out in relatively dilute solutions and clean solutions. These studies have considered both thermodynamic and kinetic controls. Most have not considered the water itself. Is the water a passive bystander, or is it intimately a participant in the mineral ion densification reaction? A wide range of experiments show that the mineralization pathways proceed through a series of densification stages with intermediates, such as a "dense liquid" phase and the prenucleation clusters that form within it. This is in contrast to the idea of a single step phase transition, but consistent with the Gibbs concept of discontinuous phase transitions from supersaturated mother liquor to crystal. Further changes in the water structure at every surface and interface during densification guides the free energy trajectory leading to the crystalline state. In vertebrates, mineralization takes place in a hydrated collagen matrix, thus water must be considered as a direct participant. Although different in detail, the crystallization of calcium phosphates, as apatite, and calcium carbonates, as calcite, are mechanistically identical from the viewpoint of water.

  20. Gold ink coating of thermocouple sheaths

    DOEpatents

    Ruhl, H. Kenneth

    1992-01-01

    A method is provided for applying a gold ink coating to a thermocouple sheath which includes the steps of electropolishing and oxidizing the surface of the thermocouple sheath, then dipping the sheath into liquid gold ink, and finally heat curing the coating. The gold coating applied in this manner is highly reflective and does not degrade when used for an extended period of time in an environment having a temperature over 1000.degree. F. Depending on the application, a portion of the gold coating covering the tip of the thermocouple sheath is removed by abrasion.

  1. Sheath insulator test thermal analysis

    NASA Astrophysics Data System (ADS)

    Lee, Celia C. M.

    Thermal models were developed for Instrumented Fast Reactor Component Sheath Insulator (IFAC-SI) test to aid in the design and fabrication of the experiment which is part of the Thermionic Fuel Element Verification Program. The actual experiment with two heat pipes in one test capsule is described by Miskolczy and Lee (1990). Two-dimensional finite element models were used in conjunction with other explicit programs to determine the necessary fin design and argon filling conditions of the vapor controlled heat pipes used to maintain desired operating temperatures. Four two-dimensional finite element models were developed: an axisymmetric capsule model; a radial sheath insulator model; a radial fin model, and an axial fin model. All finite element models were verified by comparing results between models and explicit one-dimensional heat-flow calculations. This thermal analysis package of 2D FEMs and explicit programs predicts the best geometry and placement of fins to compensate for uncertainties from internal gamma heating, emissivity of niobium, and outer sodium temperature.

  2. Sheath insulator test thermal analysis

    NASA Astrophysics Data System (ADS)

    Lee, Celia C. M.

    1991-01-01

    Thermal models were developed for Instrumented Fast Reactor Component Sheath Insulator (IFAC-SI) test to aid in the design and fabrication of the experiment which is part of the Thermionic Fuel Element (TFE) Verification Program. The actual experiment with two heat pipes in one test capsule is described by Miskolczy and Lee (1990). Two-dimensional finite element models were used in conjunction with other explicit programs to determine the necessary fin design and argon filling conditions of the vapor controlled heat pipes used to maintain desired operating temperatures. Four two-dimensional finite element models were developed: an axisymmetric capsule model; a radial sheath insulator model; a radial fin model, and an axial fin model. All finite element models were verified by comparing results between models and explicity one-dimensional heat-flow calculations. Additional programs were written to calculate the thermal expansion of the capsule components and argon volumes for operating temperatures. This thermal analysis package of two-dimensional finite element models and explicit programs predicts the best geometry and placement of fins to compensate for uncertainties from internal gamma heating, emissivity of niobium, and outer sodium temperature.

  3. Multiple Fibromas of Tendon Sheath: Unusual Presentation

    PubMed Central

    Park, Se Young; Jin, Seon Pil; Yeom, Bora; Kim, Shin Woo; Cho, So Yun

    2011-01-01

    Fibroma of the tendon sheath is an uncommon soft tissue tumor presenting as a solitary, slow-growing, firm, painless, small nodule, which shows strong attachment to the tendon or tendon sheath. It is usually localized on fingers and hand tendons in adults between the age of 20 and 40 years old. This case concerns a 61-year-old man presenting with a 5-year history of multiple cutaneous nodules on both palms and soles. Skin biopsy confirmed fibroma of the tendon sheath. Blood tests showed a high titer of rheumatoid factor and positivity to anti-nuclear antibody. No case of fibroma of the tendon sheath occurring multifocally on both palms and soles has been previously reported. Herein, we report on a very rare case of multiple fibromas of the tendon sheath arising from palms and soles, which supports the pathogenetic hypothesis that this tumor may be a reactive process rather than a true neoplasm. PMID:22028571

  4. Disposable sheath that facilitates endoscopic Raman spectroscopy.

    PubMed

    Wang, Wenbo; Short, Michael; Tai, Isabella T; Zeng, Haishan

    2016-02-01

    In vivo endoscopic Raman spectroscopy of human tissue using a fiber optic probe has been previously demonstrated. However, there remain several technical challenges, such as a robust control over the laser radiation dose and measurement repeatability during endoscopy. A decrease in the signal to noise was also observed due to aging of Raman probe after repeated cycles of harsh reprocessing procedures. To address these issues, we designed and tested a disposable, biocompatible, and sterile sheath for use with a fiber optic endoscopic Raman probe. The sheath effectively controls contamination of Raman probes between procedures, greatly reduces turnaround time, and slows down the aging of the Raman probes. A small optical window fitted at the sheath cap maintained the measurement distance between Raman probe end and tissue surface. To ensure that the sheath caused a minimal amount of fluorescence and Raman interference, the optical properties of materials for the sheath, optical window, and bonding agent were studied. The easy-to-use sheath can be manufactured at a moderate cost. The sheath strictly enforced a maximum permissible exposure standard of the tissue by the laser and reduced the spectral variability by 1.5 to 8.5 times within the spectral measurement range.

  5. Optical properties of nonextensive inhomogeneous plasma sheath

    NASA Astrophysics Data System (ADS)

    Mousavi, A.; Esfandiari-Kalejahi, A.; Akbari-Moghanjoughi, M.

    2016-07-01

    Propagation of electromagnetic wave through an inhomogeneous magnetized nonextensive plasma sheath is numerically examined for a realistic density profile of a reentry problem around a hypersonic vehicle. The effect of nonextensivity and inhomogeneity on radio wave communication is studied parametrically. Variation of reflection and transmission coefficients, total attenuation, and total phase shift over the plasma sheath with respect to the strength of applied magnetic field are derived and compared for different values of q-nonextensive parameter. The obtained results for inhomogeneous plasma sheath are compared with previously obtained results of authors for homogeneous plasma sheath. The comparison shows that radio communication in the inhomogeneous plasma sheath is more advantageous than that in the homogeneous case. The transmission coefficient of a plasma sheath with superthermal electrons ( /1 3 < q < 1 ) has larger value compared to that with q > 1. Moreover, for ω c e > ω , the minimum value of total attenuation corresponds to the range /1 3 < q < 1 . An interesting result is that nonextensivity effect on wave propagation in plasma sheath depends on the strength of the ambient magnetic field. The effect of nonextensivity on attenuation coefficient is found to be negligible for ω c e < ω while it is significant for ω c e > ω .

  6. Disposable sheath that facilitates endoscopic Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Wenbo; Short, Michael; Tai, Isabella T.; Zeng, Haishan

    2016-02-01

    In vivo endoscopic Raman spectroscopy of human tissue using a fiber optic probe has been previously demonstrated. However, there remain several technical challenges, such as a robust control over the laser radiation dose and measurement repeatability during endoscopy. A decrease in the signal to noise was also observed due to aging of Raman probe after repeated cycles of harsh reprocessing procedures. To address these issues, we designed and tested a disposable, biocompatible, and sterile sheath for use with a fiber optic endoscopic Raman probe. The sheath effectively controls contamination of Raman probes between procedures, greatly reduces turnaround time, and slows down the aging of the Raman probes. A small optical window fitted at the sheath cap maintained the measurement distance between Raman probe end and tissue surface. To ensure that the sheath caused a minimal amount of fluorescence and Raman interference, the optical properties of materials for the sheath, optical window, and bonding agent were studied. The easy-to-use sheath can be manufactured at a moderate cost. The sheath strictly enforced a maximum permissible exposure standard of the tissue by the laser and reduced the spectral variability by 1.5 to 8.5 times within the spectral measurement range.

  7. Theory of the electron sheath and presheath

    SciTech Connect

    Scheiner, Brett; Baalrud, Scott D.; Yee, Benjamin T.; Hopkins, Matthew M.; Barnat, Edward V.

    2015-12-30

    Here, electron sheaths are commonly found near Langmuir probes collecting the electron saturation current. The common assumption is that the probe collects the random flux of electrons incident on the sheath, which tacitly implies that there is no electron presheath and that the flux collected is due to a velocity space truncation of the electron velocity distribution function (EVDF). This work provides a dedicated theory of electron sheaths, which suggests that they are not so simple. Motivated by EVDFs observed in particle-in-cell(PIC) simulations, a 1D model for the electron sheath and presheath is developed. In the model, under low temperature plasma conditions (Te >> Ti), an electron pressure gradient accelerates electrons in the presheath to a flow velocity that exceeds the electron thermal speed at the sheath edge. This pressure gradient generates large flow velocities compared to what would be generated by ballistic motion in response to the electric field. It is found that in many situations, under common plasma conditions, the electron presheath extends much further into the plasma than an analogous ion presheath. PIC simulations reveal that the ion density in the electron presheath is determined by a flow around the electron sheath and that this flow is due to 2D aspects of the sheath geometry. Simulations also indicate the presence of ion acoustic instabilities excited by the differential flow between electrons and ions in the presheath, which result in sheath edge fluctuations. The 1D model and time averaged PIC simulations are compared and it is shown that the model provides a good description of the electron sheath and presheath.

  8. Theory of the electron sheath and presheath

    DOE PAGES

    Scheiner, Brett; Baalrud, Scott D.; Yee, Benjamin T.; Hopkins, Matthew M.; Barnat, Edward V.

    2015-12-30

    Here, electron sheaths are commonly found near Langmuir probes collecting the electron saturation current. The common assumption is that the probe collects the random flux of electrons incident on the sheath, which tacitly implies that there is no electron presheath and that the flux collected is due to a velocity space truncation of the electron velocity distribution function (EVDF). This work provides a dedicated theory of electron sheaths, which suggests that they are not so simple. Motivated by EVDFs observed in particle-in-cell(PIC) simulations, a 1D model for the electron sheath and presheath is developed. In the model, under low temperaturemore » plasma conditions (Te >> Ti), an electron pressure gradient accelerates electrons in the presheath to a flow velocity that exceeds the electron thermal speed at the sheath edge. This pressure gradient generates large flow velocities compared to what would be generated by ballistic motion in response to the electric field. It is found that in many situations, under common plasma conditions, the electron presheath extends much further into the plasma than an analogous ion presheath. PIC simulations reveal that the ion density in the electron presheath is determined by a flow around the electron sheath and that this flow is due to 2D aspects of the sheath geometry. Simulations also indicate the presence of ion acoustic instabilities excited by the differential flow between electrons and ions in the presheath, which result in sheath edge fluctuations. The 1D model and time averaged PIC simulations are compared and it is shown that the model provides a good description of the electron sheath and presheath.« less

  9. Theory of the electron sheath and presheath

    NASA Astrophysics Data System (ADS)

    Scheiner, Brett; Baalrud, Scott D.; Yee, Benjamin T.; Hopkins, Matthew M.; Barnat, Edward V.

    2015-12-01

    Electron sheaths are commonly found near Langmuir probes collecting the electron saturation current. The common assumption is that the probe collects the random flux of electrons incident on the sheath, which tacitly implies that there is no electron presheath and that the flux collected is due to a velocity space truncation of the electron velocity distribution function (EVDF). This work provides a dedicated theory of electron sheaths, which suggests that they are not so simple. Motivated by EVDFs observed in particle-in-cell (PIC) simulations, a 1D model for the electron sheath and presheath is developed. In the model, under low temperature plasma conditions ( Te≫Ti ), an electron pressure gradient accelerates electrons in the presheath to a flow velocity that exceeds the electron thermal speed at the sheath edge. This pressure gradient generates large flow velocities compared to what would be generated by ballistic motion in response to the electric field. It is found that in many situations, under common plasma conditions, the electron presheath extends much further into the plasma than an analogous ion presheath. PIC simulations reveal that the ion density in the electron presheath is determined by a flow around the electron sheath and that this flow is due to 2D aspects of the sheath geometry. Simulations also indicate the presence of ion acoustic instabilities excited by the differential flow between electrons and ions in the presheath, which result in sheath edge fluctuations. The 1D model and time averaged PIC simulations are compared and it is shown that the model provides a good description of the electron sheath and presheath.

  10. Effects of electron emission on sheath potential

    NASA Astrophysics Data System (ADS)

    Dow, Ansel; Khrabrov, Alexander; Kaganovich, Igor; Schamis, Hanna

    2015-11-01

    We investigate the potential profile of a sheath under the influence of surface electron emission. The plasma and sheath profiles are simulated using the Large Scale Plasma (LSP) particle-in-cell code. Using one dimensional models we corroborate the analytical relationship between sheath potential and plasma electron and emitted electron temperatures derived earlier. This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No. DE-AC02-09CH11466.

  11. Side-welded fast response sheathed thermocouple

    DOEpatents

    Carr, Kenneth R.

    1981-01-01

    A method of fabricating the measuring junction of a grounded-junction sheathed thermocouple to obtain fast time response and good thermal cycling performance is provided. Slots are tooled or machined into the sheath wall at the measuring junction, the thermocouple wires are laser-welded into the slots. A thin metal closure cap is then laser-welded over the end of the sheath. Compared to a conventional grounded-junction thermocouple, the response time is 4-5 times faster and the thermal shock and cycling capabilities are substantially improved.

  12. Side-welded fast response sheathed thermocouple

    DOEpatents

    Carr, K.R.

    A method of fabricating the measuring junction of a grounded-junction sheathed thermocouple to obtain fast time response and good thermal cycling performance is provided. Slots are tooled or machined into the sheath wall at the measuring junction, the thermocouple wires are laser-welded into the slots. A thin metal closure cap is then laser-welded over the end of the sheath. Compared to a conventional grounded-junction thermocouple, the response time is 4 to 5 times faster and the thermal shock and cycling capabilities are substantially improved.

  13. Laboratory simulations of photoelectron sheaths

    NASA Astrophysics Data System (ADS)

    Dove, A.; Wang, X.; Robertson, S. H.; Poppe, A.; Horanyi, M.

    2011-12-01

    Surfaces of airless natural bodies, such as the Moon and asteroids, and spacecraft in space are exposed to solar ultraviolet radiation that creates a photoelectron sheath that dominates the near-surface plasma environment. In order to reproduce and investigate this photoelectron layer, we conduct experiments in vacuum with Xe excimer lamps that emit UV light at ~172 nm (7.21 eV) which is of sufficient intensity to create a photoelectron layer with a characteristic length on the order of several centimeters. We utilize surfaces, such as Zr and CeO2 that have a low work function and a high photoelectron emission yield to maximize the electron density. In order to repel stray electrons that are produced by other surfaces in the chamber, and to define a reference potential, a negatively biased grid is placed 7.5 cm above the surface. The surface and the grid are used as a retarding potential analyzer to determine the energy distribution of the electrons emitted from the surface. When the grid is biased to -20 V, the emitted electrons have an approximately Maxwellian energy distribution with a characteristic temperature of 1.4 ± 0.3 eV. A Langmuir probe is also used as a diagnostic tool to find the effective electron temperature and electron density within the pure electron plasma, and is moved in order to probe different heights above the surface. The derived densities and potentials are compared with those predicted by 1-D PIC code simulations.

  14. Malignant Peripheral Nerve Sheath Tumors.

    PubMed

    Durbin, Adam D; Ki, Dong Hyuk; He, Shuning; Look, A Thomas

    2016-01-01

    Malignant peripheral nerve sheath tumors (MPNST) are tumors derived from Schwann cells or Schwann cell precursors. Although rare overall, the incidence of MPNST has increased with improved clinical management of patients with the neurofibromatosis type 1 (NF1) tumor predisposition syndrome. Unfortunately, current treatment modalities for MPNST are limited, with no targeted therapies available and poor efficacy of conventional radiation and chemotherapeutic regimens. Many murine and zebrafish models of MPNST have been developed, which have helped to elucidate the genes and pathways that are dysregulated in MPNST tumorigenesis, including the p53, and the RB1, PI3K-Akt-mTOR, RAS-ERK and Wnt signaling pathways. Preclinical results have suggested that new therapies, including mTOR and ERK inhibitors, may synergize with conventional chemotherapy in human tumors. The discovery of new genome editing technologies, like CRISPR-cas9, and their successful application to the zebrafish model will enable rapid progress in the faithful modeling of MPNST molecular pathogenesis. The zebrafish model is especially suited for high throughput screening of new targeted therapeutics as well as drugs approved for other purposes, which may help to bring enhanced treatment modalities into human clinical trials for this devastating disease. PMID:27165368

  15. Dynamics of dust in the sheath of weakly electronegative plasmas

    SciTech Connect

    Wang Zhengxiong; Wang Xiaogang; Liu Jinyuan; Liu Yue

    2005-01-15

    The dynamics of dust in the sheath of weakly electronegative plasmas are investigated with the single dust model as well as the self-consistently variable dust charge. It is shown that when the dust particles enter the sheath region from the sheath edge with different initial velocities they may display different motion states: levitation in the sheath, returning from the sheath edge, and traversing the sheath region, under action of electrostatic, gravitational, ion-drag, and neutral collision forces. Furthermore, the electronegativity also plays an important role in the dust particle motion states in the sheath besides affecting the distributions of the spatial potential and the charging of the dust particles.

  16. Instrumented Sheath Insulator Experiment (IFAC-SI)

    NASA Astrophysics Data System (ADS)

    Lee, Celia; Miskolczy, Gabor; Lieb, David P.; Witt, Tony

    The Instrumented Fast-Reactor Accelerated Component-Sheath Insulator test (IFAC-SI) is a key experiment of the Thermionic Fuel Element Verification Program designed to allow continuous monitoring of sheath insulator specimens with an applied voltage during the in-reactor test. This paper describes the IFAC-SI experiment test setting, including shear insulator samples, heat pipes, fins, and enclosing container, and discusses the thermal models and their effects on the experimental design.

  17. Protective sheath for a continuous measurement thermocouple

    DOEpatents

    Phillippi, R.M.

    1991-12-03

    Disclosed is a protective thermocouple sheath of a magnesia graphite refractory material for use in continuous temperature measurements of molten metal in a metallurgical ladle and having a basic slag layer thereon. The sheath includes an elongated torpedo-shaped sheath body formed of a refractory composition and having an interior borehole extending axially therethrough and adapted to receive a thermocouple. The sheath body includes a lower end which is closed about the borehole and forms a narrow, tapered tip. The sheath body also includes a first body portion integral with the tapered tip and having a relatively constant cross section and providing a thin wall around the borehole. The sheath body also includes a second body portion having a relatively constant cross section larger than the cross section of the first body portion and providing a thicker wall around the borehole. The borehole terminates in an open end at the second body portion. The tapered tip is adapted to penetrate the slag layer and the thicker second body portion and its magnesia constituent material are adapted to withstand chemical attack thereon from the slag layer. The graphite constituent improves thermal conductivity of the refractory material and, thus, enhances the thermal responsiveness of the device. 4 figures.

  18. Protective sheath for a continuous measurement thermocouple

    DOEpatents

    Phillippi, R. Michael

    1991-01-01

    Disclosed is a protective thermocouple sheath of a magnesia graphite refractory material for use in continuous temperature measurements of molten metal in a metallurgical ladle and having a basic slag layer thereon. The sheath includes an elongated torpedo-shaped sheath body formed of a refractory composition and having an interior borehole extending axially therethrough and adapted to receive a thermocouple. The sheath body includes a lower end which is closed about the borehole and forms a narrow, tapered tip. The sheath body also includes a first body portion integral with the tapered tip and having a relatively constant cross section and providing a thin wall around the borehole. The sheath body also includes a second body portion having a relatively constant cross section larger than the cross section of the first body portion and providing a thicker wall around the borehole. The borehole terminates in an open end at the second body portion. The tapered tip is adapted to penetrate the slag layer and the thicker second body portion and its magnesia constituent material are adapted to withstand chemical attack thereon from the slag layer. The graphite constituent improves thermal conductivity of the refractory material and, thus, enhances the thermal responsiveness of the device.

  19. Dust particle dynamics in magnetized plasma sheath

    SciTech Connect

    Davoudabadi, M.; Mashayek, F.

    2005-07-15

    In this paper, the structure of a plasma sheath in the presence of an oblique magnetic field is investigated, and dynamics of a dust particle embedded in the sheath is elaborated. To simulate the sheath, a weakly collisional two-fluid model is implemented. For various magnitudes and directions of the magnetic field and chamber pressures, different plasma parameters including the electron and ion densities, ion flow velocity, and electric potential are calculated. A complete set of forces acting on the dust particle originating from the electric field in the sheath, the static magnetic field, gravity, and ion and neutral drags is taken into account. Through the trapping potential energy, the particle stable and unstable equilibria are studied while the particle is stationary inside the sheath. Other features such as the possibility of the dust levitation and trapping in the sheath, and the effect of the Lorentz force on the charged dust particle motion are also examined. An interesting feature is captured for the variation of the particle charge as a function of the magnetic field magnitude.

  20. Theory of the Electron Sheath and Presheath

    NASA Astrophysics Data System (ADS)

    Scheiner, Brett; Baalrud, Scott; Yee, Benjamin; Hopkins, Matthew; Barnat, Edward

    2015-09-01

    Electron sheaths are commonly found near Langmuir probes collecting the electron saturation current. The common assumption is that the probe collects the random flux of electrons incident on the sheath, which tacitly implies that there is no electron presheath and that the flux collected is due to a velocity space truncation of the velocity distribution function (VDF). This work provides a dedicated theory of electron sheaths, which suggests that electron sheaths are not so simple. Motivated by VDFs observed in recent Particle-In-Cell (PIC) simulations, we develop a 1D model for the electron sheath and presheath. In the model, under low temperature plasma conditions, an electron pressure gradient accelerates electrons in the presheath to a flow velocity that exceeds the electron thermal speed at the sheath edge. This pressure gradient allows the generation of large flows compared to those that would be generated by the electric field alone. It is due to this pressure gradient that the electron presheath extends much further into the plasma (nominally by a factor of √{mi /me }) than an analogous ion presheath. Results of the model are compared with PIC simulations. This work was supported by the Office of Fusion Energy Science at the U.S. Department of Energy under contract DE-AC04-94SL85000 and by the Office of Science Graduate Student Research (SCGSR) program under Contract Number DE-AC05-06OR23100.

  1. How to Patch Active Plasma and Collisionless Sheath: Practical Guide

    SciTech Connect

    Kaganovich, Igor D.

    2002-08-22

    Most plasmas have a very thin sheath compared with the plasma dimension. This necessitates separate calculations of the plasma and sheath. The Bohm criterion provides the boundary condition for calculation of plasma profiles. To calculate sheath properties, a value of electric field at the plasma-sheath interface has to be specified in addition to the Bohm criterion. The value of the boundary electric field and robust procedure to approximately patch plasma and collisionless sheath with a very good accuracy are reported.

  2. Polarization force-induced changes in the dust sheath formation

    SciTech Connect

    Mayout, Saliha; Bentabet, Karima; Tribeche, Mouloud

    2015-09-15

    The modifications arising in the dusty plasma sheath structure due to the presence of polarization forces acting on the dust grains are investigated. The corresponding appropriate Bohm criterion for sheath formation is obtained. It is found that the critical Mach number, beyond which the dusty plasma electrostatic sheath sets in, decreases whenever the polarization effects become important. In addition, when the polarization force dominates over the electrical one, the dust plasma sheath cannot set in. This happens whenever the dust grain size exceeds a critical threshold. Moreover, the sheath electrostatic potential-gradient becomes abruptly steep, and the sheath thickness becomes broader as the polarization force effects strengthen.

  3. 56. POWDER MAGAZINE, VIEW OF INTACT WOOD SHEATHING ON THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    56. POWDER MAGAZINE, VIEW OF INTACT WOOD SHEATHING ON THE SOUTHWEST REAR VENTILATION PASSAGE. (SHEATHING HELP CONTROL HUMIDITY AND DECREASE DANGER OF MAETAL STRIKING STONE AND SPARKING.) - Fort Monroe, Fortress, Hampton, Hampton, VA

  4. ULTRASTRUCTURE OF THE PRAWN NERVE SHEATHS

    PubMed Central

    Doggenweiler, C. F.; Heuser, John E.

    1967-01-01

    The sheaths from freshly teased nerve fibers of the prawn exhibit a positive radial birefringence, consistent with their EM appearance as highly organized laminated structures composed of numerous thin cytoplasmic sheets or laminae bordered by unit membranes and arranged concentrically around the axon. The closely apposed membranes in these sheaths are fragile and often break down into rows of vesicles during fixation. Desmosome-like attachment zones occur in many regions of the sheath. The membranes within these zones resist vesiculation and thereby provide a "control" region for relating the type of vesicles formed in the fragile portions of the sheaths to the specific fixation conditions. It is proposed that during fixation the production of artifactual vesicles is governed by an interplay of three factors: (a) direct chemical action of the fixative on the polar strata of adjacent unit membranes, (b) osmotic forces applied to membranes during fixation, and (c) the pre-existing natural relations between adjacent membranes. It is found that permanganate best preserves the continuity of the membranes but will still produce vesicles if the fixative exerts severe osmotic forces. These results support other reports (19) of the importance of comparing tissues fixed by complementary procedures so that systematic artifacts will not be described as characteristic of the natural state. PMID:4166578

  5. Radio-frequency sheath-plasma interactions with magnetic field tangency points along the sheath surface

    SciTech Connect

    Kohno, H.; Myra, J. R.; D'Ippolito, D. A.

    2013-08-15

    Computer simulations of radio-frequency (RF) waves propagating across a two-dimensional (2D) magnetic field into a conducting boundary are described. The boundary condition for the RF fields at the metal surface leads to the formation of an RF sheath, which has previously been studied in one-dimensional models. In this 2D study, it is found that rapid variation of conditions along the sheath surface promote coupling of the incident RF branch (either fast or slow wave) to a short-scale-length sheath-plasma wave (SPW). The SPW propagates along the sheath surface in a particular direction dictated by the orientation of the magnetic field with respect to the surface, and the wave energy in the SPW accumulates near places where the background magnetic field is tangent to the surface.

  6. Radio-frequency sheath-plasma interactions with magnetic field tangency points along the sheath surface

    NASA Astrophysics Data System (ADS)

    Kohno, H.; Myra, J. R.; D'Ippolito, D. A.

    2013-08-01

    Computer simulations of radio-frequency (RF) waves propagating across a two-dimensional (2D) magnetic field into a conducting boundary are described. The boundary condition for the RF fields at the metal surface leads to the formation of an RF sheath, which has previously been studied in one-dimensional models. In this 2D study, it is found that rapid variation of conditions along the sheath surface promote coupling of the incident RF branch (either fast or slow wave) to a short-scale-length sheath-plasma wave (SPW). The SPW propagates along the sheath surface in a particular direction dictated by the orientation of the magnetic field with respect to the surface, and the wave energy in the SPW accumulates near places where the background magnetic field is tangent to the surface.

  7. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  8. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  9. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  10. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  11. 30 CFR 75.1314 - Sheathed explosive units.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Sheathed explosive units. 75.1314 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Explosives and Blasting § 75.1314 Sheathed explosive units. (a) A separate instantaneous detonator shall be used to fire each sheathed explosive...

  12. Optic Nerve Sheath Mechanics in VIIP Syndrome

    NASA Technical Reports Server (NTRS)

    Raykin, Julia; Feola, Andrew; Gleason, Rudy; Mulugeta, Lealem; Myers, Jerry; Nelson, Emily; Samuels, Brian; Ethier, C. Ross

    2015-01-01

    Visual Impairment and Intracranial Pressure (VIIP) syndrome results in a loss of visual function and occurs in astronauts following long-duration spaceflight. Understanding the mechanisms that lead to the ocular changes involved in VIIP is of critical importance for space medicine research. Although the exact mechanisms of VIIP are not yet known, it is hypothesized that microgravity-induced increases in intracranial pressures (ICP) drive the remodeling of the optic nerve sheath, leading to compression of the optic nerve which in turn may reduce visual acuity. Some astronauts present with a kink in the optic nerve after return to earth, suggesting that tissue remodeling in response to ICP increases may be taking place. The goal of this work is to characterize the mechanical properties of the optic nerve sheath (dura mater) to better understand its biomechanical response to increased ICP.

  13. Experimental Investigations of the Lunar Photoelectron Sheath

    NASA Astrophysics Data System (ADS)

    Dove, A.; Sternovsky, Z.; Wang, X.; Robertson, S. H.; Lapanse, C.; Horanyi, M.; Collette, A.

    2010-12-01

    Solar ultraviolet radiation incident upon the dayside lunar surface produces a photoelectron gas that dominates the near-surface plasma environment, with a typical density of 60 cm-3 and a characteristic scale-length of ~1 m. It has traditionally been difficult to produce a photoelectron gas with sufficient density in a laboratory settings to study its properties. In our initial experiments, the characterization of the photoelectron density above a Zr surface (work function W=4.4 eV) illuminated by Xe excimer lamps (peak emission at a wavelength of 172 nm) indicated that a sheath with a Debye length on the order of 10 cm formed. We characterize the photoelectron population above the surface by utilizing an emissive probe to map the electric potential distribution above the surface, and a Langmuir probe to determine the number density and temperature of the photoelectrons. A grid is placed 7.5 cm above the Zr surface to repel photoelectrons emitted from the chamber walls. Emissive probe measurements show a potential dip of about 2 V extending ~1 cm above the zirconium surface. The size of this potential well is dependent on the number of lamps illuminating the surface, as the density of photoelectrons above the surface increases with greater illumination. The electrons in the sheath have a Maxwellian distribution with an electron temperature around 1 eV (maximum energies are expected to be approximately 2.8 eV). We will use this experimental apparatus to characterize the photoelectron sheath above other surfaces; powders, such as CeO2 have similar work functions, but different photoelectric yields. Lunar soil simulants are expected to have approximately an order of magnitude smaller yield than metallic surfaces, which will act to increase the characteristic length of the photoelectron sheath above the surface. The experiments and accompanying computer simulations are used to guide the development of new instrument concepts for future in situ plasma measurements on

  14. Two Types of Magnetohydrodynamic Sheath Jets

    NASA Astrophysics Data System (ADS)

    Kaburaki, Osamu

    2009-06-01

    Recent observations of astrophysical jets emanating from various galactic nuclei strongly suggest that a double-layered structure, or a spine-sheath structure, is likely to be their common feature. We propose that such a sheath jet structure can be formed magnetohydrodynamically within a valley of the magnetic pressures, which is formed between the peaks due to the poloidal and toroidal components, with the centrifugal force acting on the rotating sheath plasma being balanced by the hoop stress of the toroidal field. The poloidal field concentrated near the polar axis is maintained by a converging plasma flow toward the jet region, and the toroidal field is developed outside the jet cone owing to the poloidal current circulating through the jet. Under such situations, the set of magnetohydrodynamic (MHD) equations allows two main types of solutions, at least, in the region far from the footpoint. The first type solution describes the jets of marginally bound nature. This type is realized when the jet temperature decreases like a virial one, and neither the pressure-gradient nor the MHD forces, which are both determined consistently, cannot completely overcome the gravity, even at infinity. The second type is realized under an isothermal situation, and the gravity is cancelled exactly by the pressure-gradient force. Hence, the jets of this type are accelerated purely by the MHD force. It is also suggested that these two types correspond, respectively, to the jets from type I and II radio galaxies in the Fanaroff-Riley classification.

  15. Radio frequency sheaths in an oblique magnetic field

    SciTech Connect

    Myra, J. R.; D'Ippolito, D. A.

    2015-06-15

    The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describes the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle θ, assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numerically to obtain the rectified (dc) voltage, the rf voltage across the sheath, and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general, the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall.

  16. Radio frequency sheaths in an oblique magnetic field

    DOE PAGES

    Myra, James R.; D'Ippolito, Daniel A.

    2015-06-01

    The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describe the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle, θ assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numericallymore » to obtain the rectified (dc) voltage, the rf voltage across the sheath and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall.« less

  17. Radio frequency sheaths in an oblique magnetic field

    SciTech Connect

    Myra, James R.; D'Ippolito, Daniel A.

    2015-06-01

    The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describe the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle, θ assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numerically to obtain the rectified (dc) voltage, the rf voltage across the sheath and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall.

  18. Optic Nerve Sheath Mechanics in VIIP Syndrome

    NASA Technical Reports Server (NTRS)

    Raykin, Julia; Forte, Taylor E.; Wang, Roy; Feola, Andrew; Samuels, Brian; Myers, Jerry; Nelson, Emily; Gleason, Rudy; Ethier, C. Ross

    2016-01-01

    Visual Impairment Intracranial Pressure (VIIP) syndrome is a major concern in current space medicine research. While the exact pathology of VIIP is not yet known, it is hypothesized that the microgravity-induced cephalad fluid shift increases intracranial pressure (ICP) and drives remodeling of the optic nerve sheath. To investigate this possibility, we are culturing optic nerve sheath dura mater samples under different pressures and investigating changes in tissue composition. To interpret results from this work, it is essential to first understand the biomechanical response of the optic nerve sheath dura mater to loading. Here, we investigated the effects of mechanical loading on the porcine optic nerve sheath.Porcine optic nerves (number: 6) were obtained immediately after death from a local abattoir. The optic nerve sheath (dura mater) was isolated from the optic nerve proper, leaving a hollow cylinder of connective tissue that was used for biomechanical characterization. We developed a custom mechanical testing system that allowed for unconfined lengthening, twisting, and circumferential distension of the dura mater during inflation and under fixed axial loading. To determine the effects of variations in ICP, the sample was inflated (0-60 millimeters Hg) and circumferential distension was simultaneously recorded. These tests were performed under variable axial loads (0.6 grams - 5.6 grams at increments of 1 gram) by attaching different weights to one end of the dura mater. Results and Conclusions: The samples demonstrated nonlinear behavior, similar to other soft connective tissue (Figure 1). Large increases in diameter were observed at lower transmural pressures (approximately 0 to 5 millimeters Hg), whereas only small diameter changes were observed at higher pressures. Particularly interesting was the existence of a cross-over point at a pressure of approximately 11 millimeters Hg. At this pressure, the same diameter is obtained for all axial loads applied

  19. Sheath insulator final test report, TFE Verification Program

    SciTech Connect

    Not Available

    1994-07-01

    The sheath insulator in a thermionic cell has two functions. First, the sheath insulator must electrically isolate the collector form the outer containment sheath tube that is in contact with the reactor liquid metal coolant. Second, The sheath insulator must provide for high uniform thermal conductance between the collector and the reactor coolant to remove away waste heat. The goals of the sheath insulator test program were to demonstrate that suitable ceramic materials and fabrication processes were available, and to validate the performance of the sheath insulator for TFE-VP requirements. This report discusses the objectives of the test program, fabrication development, ex-reactor test program, in-reactor test program, and the insulator seal specifications.

  20. Kinetic model for the collisionless sheath of a collisional plasma

    NASA Astrophysics Data System (ADS)

    Tang, Xian-Zhu; Guo, Zehua

    2016-08-01

    Collisional plasmas typically have mean-free-path still much greater than the Debye length, so the sheath is mostly collisionless. Once the plasma density, temperature, and flow are specified at the sheath entrance, the profile variation of electron and ion density, temperature, flow speed, and conductive heat fluxes inside the sheath is set by collisionless dynamics, and can be predicted by an analytical kinetic model distribution. These predictions are contrasted here with direct kinetic simulations, showing good agreement.

  1. Sheath structure in electronegative plasmas with finite positive ion temperature

    NASA Astrophysics Data System (ADS)

    Palop, J. I. Fernández; Ballesteros, J.; Hernández, M. A.; Crespo, R. Morales; del Pino, S. Borrego

    2004-05-01

    An earlier theoretical work, concerning the sheath structure in electronegative plasmas, is extended to include the effect of the positive ion thermal motion. A significant change is observed in the quantities characterizing the sheath with respect to the cold ion assumption. The sheath is contracted when the positive ion thermal motion is considered causing a decrease in the sheath thickness. The ion saturation current and the floating potential are shown to be distinguished quantities in plasma diagnosis of electronegative plasmas by using plane Langmuir probes.

  2. Rarefaction solitons initiated by sheath instability

    SciTech Connect

    Levko, Dmitry

    2015-09-15

    The instability of the cathode sheath initiated by the cold energetic electron beam is studied by the one-dimensional fluid model. Numerical simulations show the generation of travelling rarefaction solitons at the cathode. It is obtained that the parameters of these solitons strongly depend on the parameters of electron beam. The “stretched” variables are derived using the small-amplitude analysis. These variables are used in order to obtain the Korteweg-de Vries equation describing the propagation of the rarefaction solitons through the plasma with cold energetic electron beam.

  3. Target normal sheath acceleration sheath fields for arbitrary electron energy distribution

    SciTech Connect

    Schmitz, Holger

    2012-08-15

    Relativistic electrons, generated by ultraintense laser pulses, travel through the target and form a space charge sheath at the rear surface which can be used to accelerate ions to high energies. If the laser pulse duration is comparable or shorter than the time needed for the electrons to travel through the target, the electrons will not have the chance to form an equilibrium distribution but must be described by a non-equilibrium distribution. We present a kinetic theory of the rear sheath for arbitrary electron distribution function f(E), where E is the electron energy, and evaluate it for different shapes of f(E). We find that the far field is mainly determined by the high energy tail of the distribution, a steep decay of f(E) for high energies results in a small electric field and vice versa. The model is extended to account for electrons escaping the sheath region thereby allowing a finite potential drop over the sheath. The consequences of the model for the acceleration of ions are discussed.

  4. The characteristics of RF modulated plasma boundary sheaths: An analysis of the standard sheath model

    NASA Astrophysics Data System (ADS)

    Naggary, Schabnam; Brinkmann, Ralf Peter

    2015-09-01

    The characteristics of radio frequency (RF) modulated plasma boundary sheaths are studied on the basis of the so-called ``standard sheath model.'' This model assumes that the applied radio frequency ωRF is larger than the plasma frequency of the ions but smaller than that of the electrons. It comprises a phase-averaged ion model - consisting of an equation of continuity (with ionization neglected) and an equation of motion (with collisional ion-neutral interaction taken into account) - a phase-resolved electron model - consisting of an equation of continuity and the assumption of Boltzmann equilibrium -, and Poisson's equation for the electrical field. Previous investigations have studied the standard sheath model under additional approximations, most notably the assumption of a step-like electron front. This contribution presents an investigation and parameter study of the standard sheath model which avoids any further assumptions. The resulting density profiles and overall charge-voltage characteristics are compared with those of the step-model based theories. The authors gratefully acknowledge Efe Kemaneci for helpful comments and fruitful discussions.

  5. CNS Myelin Sheath Lengths Are an Intrinsic Property of Oligodendrocytes.

    PubMed

    Bechler, Marie E; Byrne, Lauren; Ffrench-Constant, Charles

    2015-09-21

    Since Río-Hortega's description of oligodendrocyte morphologies nearly a century ago, many studies have observed myelin sheath-length diversity between CNS regions. Myelin sheath length directly impacts axonal conduction velocity by influencing the spacing between nodes of Ranvier. Such differences likely affect neural signal coordination and synchronization. What accounts for regional differences in myelin sheath lengths is unknown; are myelin sheath lengths determined solely by axons or do intrinsic properties of different oligodendrocyte precursor cell populations affect length? The prevailing view is that axons provide molecular cues necessary for oligodendrocyte myelination and appropriate sheath lengths. This view is based upon the observation that axon diameters correlate with myelin sheath length, as well as reports that PNS axonal neuregulin-1 type III regulates the initiation and properties of Schwann cell myelin sheaths. However, in the CNS, no such instructive molecules have been shown to be required, and increasing in vitro evidence supports an oligodendrocyte-driven, neuron-independent ability to differentiate and form initial sheaths. We test this alternative signal-independent hypothesis--that variation in internode lengths reflects regional oligodendrocyte-intrinsic properties. Using microfibers, we find that oligodendrocytes have a remarkable ability to self-regulate the formation of compact, multilamellar myelin and generate sheaths of physiological length. Our results show that oligodendrocytes respond to fiber diameters and that spinal cord oligodendrocytes generate longer sheaths than cortical oligodendrocytes on fibers, co-cultures, and explants, revealing that oligodendrocytes have regional identity and generate different sheath lengths that mirror internodes in vivo.

  6. Sheath structure transition controlled by secondary electron emission

    NASA Astrophysics Data System (ADS)

    Schweigert, I. V.; Langendorf, S. J.; Walker, M. L. R.; Keidar, M.

    2015-04-01

    In particle-in-cell Monte Carlo collision (PIC MCC) simulations and in an experiment we study sheath formation over an emissive floating Al2O3 plate in a direct current discharge plasma at argon gas pressure 10-4 Torr. The discharge glow is maintained by the beam electrons emitted from a negatively biased hot cathode. We observe three types of sheaths near the floating emissive plate and the transition between them is driven by changing the negative bias. The Debye sheath appears at lower voltages, when secondary electron emission is negligible. With increasing applied voltage, secondary electron emission switches on and a first transition to a new sheath type, beam electron emission (BEE), takes place. For the first time we find this specific regime of sheath operation near the floating emissive surface. In this regime, the potential drop over the plate sheath is about four times larger than the temperature of plasma electrons. The virtual cathode appears near the emissive plate and its modification helps to maintain the BEE regime within some voltage range. Further increase of the applied voltage U initiates the second smooth transition to the plasma electron emission sheath regime and the ratio Δφs/Te tends to unity with increasing U. The oscillatory behavior of the emissive sheath is analyzed in PIC MCC simulations. A plasmoid of slow electrons is formed near the plate and transported to the bulk plasma periodically with a frequency of about 25 kHz.

  7. Anode Sheath Switching in a Carbon Nanotube Arc Plasma

    SciTech Connect

    Abe Fetterman, Yevgeny Raitses, and Michael Keidar

    2008-04-08

    The anode ablation rate is investigated as a function of anode diameter for a carbon nanotube arc plasma. It is found that anomalously high ablation occurs for small anode diameters. This result is explained by the formation of a positive anode sheath. The increased ablation rate due to this positive anode sheath could imply greater production rate for carbon nanotubes.

  8. A generalized BC for radio-frequency sheaths

    NASA Astrophysics Data System (ADS)

    D'Ippolito, D. A.; Myra, J. R.

    2015-12-01

    A new radio-frequency (rf) sheath boundary condition (BC) is described and applied to the problem of far field sheaths. The new BC generalizes the one presently used in rf codes to include: (1) an arbitrary magnetic field angle, (2) the full complex impedance, (3) mobile ions, (4) unmagnetized ions, and (5) the magnetic pre-sheath. For a given wave-propagation (macro) problem, root-finding is used to match the impedance of the rf wave with that of the micro-sheath problem. For a model far-field sheath problem, it is shown that the structure of the (multiple) roots with the new BC is similar to that with the capacitive BC, but the location of the resonance changes when the full impedance is used.

  9. Gas insulated transmission line having low inductance intercalated sheath

    DOEpatents

    Cookson, Alan H.

    1978-01-01

    A gas insulated transmission line including an outer sheath, an inner conductor disposed within the outer sheath, and an insulating gas between the inner conductor and the outer sheath. The outer sheath comprises an insulating tube having first and second ends, and having interior and exterior surfaces. A first electrically conducting foil is secured to the interior surface of the insulating tube, is spirally wound from one tube end to the second tube end, and has a plurality of overlapping turns. A second electrically conducting foil is secured to the exterior surface of the insulating tube, and is spirally wound in the opposite direction from the first electrically conducting foil. By winding the foils in opposite directions, the inductances within the intercalated sheath will cancel each other out.

  10. An Everting Ureteral Access Sheath: Concepts and In Vitro Testing

    NASA Astrophysics Data System (ADS)

    Lee, Keith L.; Stoller, Marshall L.

    2007-04-01

    Ureteral access sheaths have been a recent innovation in facilitating ureteral stone surgery. Once properly placed, access sheaths allow the movement of ureteroscopes and other instruments through the ureter with minimal injury to the urothelium. However, there are shortcomings of the current device designs. Initial sheath placement requires significant force, and shear stress can injure the ureter. In addition, inadvertent advancement of the outer sheath without the inner introducer stylet can tear and avulse the ureter. A novel eversion design incorporating a lubricous film provides marked improvement over current access sheaths. In bench top and animal models, the eversion shealths require less force during advancement, cause less injury to the urothelial tissue, and have a lower potential of introducing extraneous materials (e.g., microbes) into a simulated urinary tract. While, the everting design provides important advantages over traditional non-everting designs, further preclinical and clinical trials are required.

  11. Similarities and distinctions of CIR and Sheath

    NASA Astrophysics Data System (ADS)

    Yermolaev, Yuri; Lodkina, Irina; Nikolaeva, Nadezhda; Yermolaev, Michael

    2016-04-01

    On the basis of OMNI data and our catalog of large scale solar wind (SW) streams during 1976-2000 [Yermolaev et al., 2009] we study the average temporal profiles for two types of compressed regions: CIR (corotating interaction region - compressed region before High Speed Stream (HSS)) and Sheath (compressed region before fast Interplanetary CMEs (ICMEs), including Magnetic Cloud (MC) and Ejecta). As have been shown by Nikolaeva et al, [2015], the efficiency of magnetic storm generation is ~50% higher for Sheath and CIR than for ICME (MC and Ejecta), i.e. reaction magnetosphere depends on type of driver. To take into account the different durations of SW types, we use the double superposed epoch analysis (DSEA) method: rescaling the duration of the interval for all types in such a manner that, respectively, beginning and end for all intervals of selected type coincide [Yermolaev et al., 2010; 2015]. Obtained data allows us to suggest that the formation of all types of compression regions has the same physical mechanism irrespective of piston (HSS or ICME) type and differences are connected with geometry and full jumps of speed in edges of compression regions. If making the natural assumption that the gradient of speed is directed approximately on normal to the piston, CIR has the largest angle between the gradient of speed and the direction of average SW speed, and ICME - the smallest angle. The work was supported by the Russian Foundation for Basic Research, projects 13-02-00158, 16-02-00125 and by Program of Presidium of the Russian Academy of Sciences. References: Nikolaeva, N. S. , Yu. I. Yermolaev, and I. G. Lodkina (2015), Modeling of the Corrected Dst* Index Temporal Profile on the Main Phase of the Magnetic Storms Generated by Different Types of Solar Wind, Cosmic Research, Vol. 53, No. 2, pp. 119-127. Yermolaev, Yu. I., N. S. Nikolaeva, I. G. Lodkina, and M. Yu. Yermolaev (2009), Catalog of Large-Scale Solar Wind Phenomena during 1976-2000, Cosmic Research

  12. Bladder outlet reconstruction: fate of the silicone sheath.

    PubMed

    Kropp, B P; Rink, R C; Adams, M C; Keating, M A; Mitchell, M E

    1993-08-01

    The placement of a 1.5 cm. wide silicone sheath around a newly constructed urethra/bladder neck to ensure maintenance of repair length and to facilitate future placement of a sphincter cuff was reported by our institution in 1985. We present our long-term followup and new recommendations for use of the silicone sheath. A total of 15 silicone sheaths was placed between March 1981 and July 1984. Of the sheaths 14 were placed at the time of urinary reconstruction around the Young-Dees-Leadbetter bladder neck repair and 1 was placed after erosion of an artificial urinary sphincter cuff. Of the 15 sheaths 10 have eroded into the urethra and 4 sheaths remain in situ. Another sheath was replaced 2 years after its original insertion with an artificial urinary sphincter cuff. Mean time to erosion was 48.2 months, with a range of 2 to 108 months. Long-term followup of 10 patients revealed that 4 ultimately required ligation of the bladder neck and construction of continent stoma after erosion, 1 is dry after placement of a bulbar artificial urinary sphincter, 2 remain dry after removal of the eroded sheath alone, 2 required bladder neck revision to achieve continence after erosion and the most recent patient remains diverted with a suprapubic tube. All 4 patients with sheaths still remaining are dry without evidence of erosion (mean duration 116 months). These long-term results using a silicone wrap around a newly constructed bladder neck reveal an unacceptably high rate of erosion. Therefore, we no longer recommend or support the use of the silicone sheath in the manner we have described for bladder neck reconstruction. PMID:8326628

  13. Identification of a Gene Essential for Sheathed Structure Formation in Sphaerotilus natans, a Filamentous Sheathed Bacterium

    PubMed Central

    Suzuki, Toshihiko; Kanagawa, Takahiro; Kamagata, Yoichi

    2002-01-01

    Sphaerotilus natans, a filamentous bacterium that causes bulking in activated sludge processes, can assume two distinct morphologies, depending on the substrate concentration for growth; in substrate-rich media it grows as single rod-shaped cells, whereas in substrate-limited media it grows as filaments. To identify genes responsible for sheath formation, we carried out transposon Tn5 mutagenesis. Of the approximately 20,000 mutants obtained, 7 did not form sheathed structures. Sequencing of the Tn5-flanking regions showed that five of the seven Tn5 insertions converged at the same open reading frame, designated sthA. The deduced amino acids encoded by sthA were found to be homologous to glycosyltransferase, which is known to be involved in linking sugars to lipid carriers during bacterial exopolysaccharide biosynthesis. Disruption of the gene of the wild-type strain by inserting a kanamycin resistance gene cassette also resulted in sheathless growth under either type of nutrient condition. These findings indicate that sthA is a crucial component responsible for sheath formation. PMID:11772646

  14. Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths

    PubMed Central

    Kunoh, Tatsuki; Hashimoto, Hideki; McFarlane, Ian R.; Hayashi, Naoaki; Suzuki, Tomoko; Taketa, Eisuke; Tamura, Katsunori; Takano, Mikio; El-Naggar, Mohamed Y.; Kunoh, Hitoshi; Takada, Jun

    2016-01-01

    Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II) to Fe(III) and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II) concentrations, Fe(III) precipitates visibly formed immediately after addition of Fe(II) to the medium, suggesting prompt abiotic oxidation of Fe(II) to Fe(III). Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III) was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II) medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter), while those in the Fe(III) medium were composed of large, aggregated particles (≥3 µm diameter) with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved) of Fe encrustation of the Leptothrix sheaths. PMID:27271677

  15. The plasma drag and dust motion inside the magnetized sheath

    SciTech Connect

    Pandey, B. P.; Vladimirov, S. V.; Samarian, A.

    2011-05-15

    The motion of micron size dust inside the sheath in the presence of an oblique magnetic field is investigated by self-consistently calculating the charge and various forces acting on the dust. It is shown that the dust trajectory inside the sheath, which is like an Archimedean spiral swinging back and forth between the wall and the plasma-sheath boundary, depends only indirectly on the orientation of the magnetic field. When the Lorentz force is smaller than the collisional momentum exchange, the dust dynamics is insensitive to the obliqueness of the magnetic field. Only when the magnetic field is strong enough, the sheath structure and, thus, the dust dynamics are significantly affected by the field orientation. Balance between the plasma drag, sheath electrostatic field, and gravity plays an important role in determining how far the dust can travel inside the sheath. The dust equilibrium point shifts closer to the wall in the presence of gravity and plasma drag. However, in the absence of plasma drag, dust can sneak back into the plasma if acted only by gravity. The implication of our results to the usability of dust as a sheath probe is discussed.

  16. Nonextensive statistics and the sheath criterion in collisional plasmas

    SciTech Connect

    Hatami, M. M.

    2015-01-15

    The Bohm criterion in an electropositive plasma containing nonextensively distributed electrons and warm ions is investigated by using a steady state two-fluid model. Taking into account the ion-neutral collisions and finite temperature of ions, a modified Bohm criterion is derived which limits both maximum and minimum allowable velocity of ions at the sheath edge (u{sub 0i}). It is found that the degree of nonextensivity of electrons (q) and temperature of positive ions (T{sub i}) affect only the lower limit of the entrance velocity of ions into the sheath while the degree of ion collisionality (α) influences both lower and upper limits of the ion velocities at the sheath edge. In addition, depending on the value of q, it is shown that the minimum velocity of positive ions at the sheath edge can be greater or smaller than its Maxwellian counterpart. Moreover, it is shown that, depending on the values of α and T{sub i}, the positive ions with subsonic velocity may enter the sheath for either q > 1 or −1 < q < 1. Finally, as a practical application, the density distribution of charged particles in the sheath region is studied for different values of u{sub 0i}, and it is shown that monotonical reduction of the positive ion density distribution occurs only when the velocity of positive ions at the sheath edge lies between two above mentioned limits.

  17. Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths.

    PubMed

    Kunoh, Tatsuki; Hashimoto, Hideki; McFarlane, Ian R; Hayashi, Naoaki; Suzuki, Tomoko; Taketa, Eisuke; Tamura, Katsunori; Takano, Mikio; El-Naggar, Mohamed Y; Kunoh, Hitoshi; Takada, Jun

    2016-01-01

    Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II) to Fe(III) and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II) concentrations, Fe(III) precipitates visibly formed immediately after addition of Fe(II) to the medium, suggesting prompt abiotic oxidation of Fe(II) to Fe(III). Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III) was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II) medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter), while those in the Fe(III) medium were composed of large, aggregated particles (≥3 µm diameter) with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved) of Fe encrustation of the Leptothrix sheaths. PMID:27271677

  18. Ion Dynamics Model for Collisionless Radio Frequency Sheaths

    NASA Technical Reports Server (NTRS)

    Bose, Deepak; Govindan, T.R.; Meyyappan, M.

    2000-01-01

    Full scale reactor model based on fluid equations is widely used to analyze high density plasma reactors. It is well known that the submillimeter scale sheath in front of a biased electrode supporting the wafer is difficult to resolve in numerical simulations, and the common practice is to use results for electric field from some form of analytical sheath model as boundary conditions for full scale reactor simulation. There are several sheath models in the literature ranging from Child's law to a recent unified sheath model [P. A. Miller and M. E. Riley, J. Appl. Phys. 82, 3689 (1997)l. In the present work, the cold ion fluid equations in the radio frequency sheath are solved numerically to show that the spatiotemporal variation of ion flux inside the sheath, commonly ignored in analytical models, is important in determining the electric field and ion energy at the electrode. Consequently, a semianalytical model that includes the spatiotemporal variation of ion flux is developed for use as boundary condition in reactor simulations. This semianalytical model is shown to yield results for sheath properties in close agreement with numerical solutions.

  19. Structural and Biochemical Analysis of the Sheath of Phormidium uncinatum

    PubMed Central

    Hoiczyk, Egbert

    1998-01-01

    The sheath of the filamentous, gliding cyanobacterium Phormidium uncinatum was studied by using light and electron microscopy. In thin sections and freeze fractures the sheath was found to be composed of helically arranged carbohydrate fibrils, 4 to 7 nm in diameter, which showed a substantial degree of crystallinity. As in all other examined motile cyanobacteria, the arrangement of the sheath fibrils correlates with the motion of the filaments during gliding motility; i.e., the fibrils formed a right-handed helix in clockwise-rotating species and a left-handed helix in counterclockwise-rotating species and were radially arranged in nonrotating cyanobacteria. Since sheaths could only be found in old immotile cultures, the arrangement seems to depend on the process of formation and attachment of sheath fibrils to the cell surface rather than on shear forces created by the locomotion of the filaments. As the sheath in P. uncinatum directly contacts the cell surface via the previously identified surface fibril forming glycoprotein oscillin (E. Hoiczyk and W. Baumeister, Mol. Microbiol. 26:699–708, 1997), it seems reasonable that similar surface glycoproteins act as platforms for the assembly and attachment of the sheaths in cyanobacteria. In P. uncinatum the sheath makes up approximately 21% of the total dry weight of old cultures and consists only of neutral sugars. Staining reactions and X-ray diffraction analysis suggested that the fibrillar component is a homoglucan that is very similar but not identical to cellulose which is cross-linked by the other detected monosaccharides. Both the chemical composition and the rigid highly ordered structure clearly distinguish the sheaths from the slime secreted by the filaments during gliding motility. PMID:9683490

  20. Absence of Debye sheaths due to secondary electron emission.

    PubMed

    Campanell, M D; Khrabrov, A V; Kaganovich, I D

    2012-06-22

    A bounded plasma where the hot electrons impacting the walls produce more than one secondary on average is studied via particle-in-cell simulation. It is found that no classical Debye sheath or space-charge-limited sheath exists. Ions are not drawn to the walls and electrons are not repelled. Hence the unconfined plasma electrons travel unobstructed to the walls, causing extreme particle and energy fluxes. Each wall has a positive charge, forming a small potential barrier or "inverse sheath" that pulls some secondaries back to the wall to maintain the zero current condition.

  1. Analytical model for the radio-frequency sheath

    NASA Astrophysics Data System (ADS)

    Czarnetzki, Uwe

    2013-12-01

    A simple analytical model for the planar radio-frequency (rf) sheath in capacitive discharges is developed that is based on the assumptions of a step profile for the electron front, charge exchange collisions with constant cross sections, negligible ionization within the sheath, and negligible ion dynamics. The continuity, momentum conservation, and Poisson equations are combined in a single integro-differential equation for the square of the ion drift velocity, the so called sheath equation. Starting from the kinetic Boltzmann equation, special attention is paid to the derivation and the validity of the approximate fluid equation for momentum balance. The integrals in the sheath equation appear in the screening function which considers the relative contribution of the temporal mean of the electron density to the space charge in the sheath. It is shown that the screening function is quite insensitive to variations of the effective sheath parameters. The two parameters defining the solution are the ratios of the maximum sheath extension to the ion mean free path and the Debye length, respectively. A simple general analytic expression for the screening function is introduced. By means of this expression approximate analytical solutions are obtained for the collisionless as well as the highly collisional case that compare well with the exact numerical solution. A simple transition formula allows application to all degrees of collisionality. In addition, the solutions are used to calculate all static and dynamic quantities of the sheath, e.g., the ion density, fields, and currents. Further, the rf Child-Langmuir laws for the collisionless as well as the collisional case are derived. An essential part of the model is the a priori knowledge of the wave form of the sheath voltage. This wave form is derived on the basis of a cubic charge-voltage relation for individual sheaths, considering both sheaths and the self-consistent self-bias in a discharge with arbitrary

  2. Electron-Hose Instability in an Annular Plasma Sheath

    SciTech Connect

    Whittum, David H.

    1999-07-08

    A relativistic electron beam propagating through an annular plasma sheath is subject to a transverse plasma-electron coupled electrostatic instability. From the linearized fluid equations, the beam-sheath interaction is resolved into three coupled equations. The corresponding wakefield is computed and the asymptotic linear evolution is noted. For illustration, numerical examples are given for a plasma accelerator employing such a sheath. While the coasting beam scalings are quite severe at low energy, single-bunch instability growth can in fact be reduced to nil, for a very high-gradient accelerator.

  3. Absence of Debye Sheaths Due to Secondary Electron Emission

    SciTech Connect

    M.D. Campanell, A. Khrabrov and I. D. Kaganovich

    2012-05-11

    A bounded plasma where the hot electrons impacting the walls produce more than one secondary on average is studied via particle-in-cell simulation. It is found that no classical Debye sheath or space-charge limited sheath exists. Ions are not drawn to the walls and electrons are not repelled. Hence the unconfined plasma electrons travel unobstructed to the walls, causing extreme particle and energy fluxes. Each wall has a positive charge, forming a small potential barrier or "inverse sheath" that pulls some secondaries back to the wall to maintain the zero current condition.

  4. Spontaneous rectus sheath hematoma in a patient treated with apixaban.

    PubMed

    Aktas, Halil; Inci, Sinan; Dogan, Pinar; Izgu, Ibrahim

    2016-02-01

    Apixaban, a non-vitamin K antagonist oral anticoagulants, is a Factor Xa inhibitor that is prescribed for the treatment of non valvular atrial fibrillation. Rectus sheath hematoma is a rare but significant complication of oral anticoagulant treatment. The important causes of rectus sheath hematoma include treatment with anticoagulants, hematologic diseases, trauma, intense physical activity, coughing, sneezing and pregnancy. In this report, we describe case of a 71-year-old woman undergoing apixaban treatment for non valvular atrial fibrillation who presented with spontaneous rectus sheath hematoma. PMID:26989650

  5. Measurement of sheath thickness at a floating potential

    SciTech Connect

    Han, Hyung-Sik; Lee, Hyo-Chang; Oh, Se-Jin; Chung, Chin-Wook

    2014-02-15

    In a cylindrical Langmuir probe measurement, ion current is collected from the surface of the sheath surrounded at probe tip, not at the surface of the probe tip. By using this, the sheath thickness can be obtained, if we know some unknown parameters, such as ion current, plasma density, and electron temperature. In this paper, we present a method to measure sheath thickness by using a wave cutoff method and a floating harmonic method. The measured result is in a good agreement with Allen-Boyd-Reynolds theory.

  6. Measurement of sheath thickness at a floating potential

    NASA Astrophysics Data System (ADS)

    Han, Hyung-Sik; Lee, Hyo-Chang; Oh, Se-Jin; Chung, Chin-Wook

    2014-02-01

    In a cylindrical Langmuir probe measurement, ion current is collected from the surface of the sheath surrounded at probe tip, not at the surface of the probe tip. By using this, the sheath thickness can be obtained, if we know some unknown parameters, such as ion current, plasma density, and electron temperature. In this paper, we present a method to measure sheath thickness by using a wave cutoff method and a floating harmonic method. The measured result is in a good agreement with Allen-Boyd-Reynolds theory.

  7. A radio-frequency sheath model for complex waveforms

    SciTech Connect

    Turner, M. M.; Chabert, P.

    2014-04-21

    Plasma sheaths driven by radio-frequency voltages occur in contexts ranging from plasma processing to magnetically confined fusion experiments. An analytical understanding of such sheaths is therefore important, both intrinsically and as an element in more elaborate theoretical structures. Radio-frequency sheaths are commonly excited by highly anharmonic waveforms, but no analytical model exists for this general case. We present a mathematically simple sheath model that is in good agreement with earlier models for single frequency excitation, yet can be solved for arbitrary excitation waveforms. As examples, we discuss dual-frequency and pulse-like waveforms. The model employs the ansatz that the time-averaged electron density is a constant fraction of the ion density. In the cases we discuss, the error introduced by this approximation is small, and in general it can be quantified through an internal consistency condition of the model. This simple and accurate model is likely to have wide application.

  8. Measure Guideline: Guidance on Taped Insulating Sheathing Drainage Planes

    SciTech Connect

    Grin, A.; Lstiburek, J.

    2014-09-01

    The goal of this research is to provide durable and long-term water management solutions using exterior insulating sheathing as part of the water management system. It is possible to tape or seal the joints in insulating sheathing to create a drainage plane and even an air control layer. There exists the material durability component of the tape as well as the system durability component being the taped insulating sheathing as the drainage plane. This measure guideline provides best practice and product recommendations from the interviewed contractors and homebuilders who collectively have a vast amount of experience. Three significant issues were discussed with the group, which are required to make taped insulating sheathing a simple, long-term, and durable drainage plane: horizontal joints should be limited or eliminated wherever possible; where a horizontal joint exists use superior materials; and frequent installation inspection and regular trade training are required to maintain proper installation.

  9. Plasma sheath multipath analysis and its effect on GNSS navigation

    NASA Astrophysics Data System (ADS)

    Du, Yongxing; Xi, Xiaoli; Song, Zhongguo; Liu, Jiangfan

    2015-11-01

    When hypersonic vehicle reenters the Earth's atmosphere, the plasma sheath will be generated by its collision with ambient air that would affect global navigation satellite system (GNSS). In order to understand such effects, the transmission coefficient of the plasma sheath has been investigated using the numerical method before. But this is found to be insufficient, for besides the attenuation on the signal energy, the multipath effect between the plasma sheath and the vehicle surface is also a serious factor, which may result in errors in pseudorange measurement and carrier phase measurement of GNSS receiver and finally affect the positioning accuracy. The multipath of the plasma sheath is analyzed by finite-difference time-domain method combined with further signal processing, and a simulation platform is established to verify this effects on positioning performance. Simulation results indicate the degradation of positioning performance when these multipath signals were present, causing position error with several meters to tens of meters.

  10. 32. DETAIL OF GEARS LOOKING NORTH WITH SHEATHING REMOVED AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    32. DETAIL OF GEARS LOOKING NORTH WITH SHEATHING REMOVED AND SHAFT OF KING GEAR BEYOND - Caleb Crosby Threshing Barn, Noeton (moved to Norris Dam State Park, Lake City), Morristown, Hamblen County, TN

  11. Morphological analysis of the sheathed flagellum of Brucella melitensis

    PubMed Central

    2010-01-01

    Background It was recently shown that B. melitensis is flagellated. However, the flagellar structure remains poorly described. Findings We analyzed the structure of the polar sheathed flagellum of B. melitensis by TEM analysis and demonstrated that the Ryu staining is a good method to quickly visualize the flagellum by optical microscopy. The TEM analysis demonstrated that an extension of the outer membrane surrounds a filament ending by a club-like structure. The ΔftcR, ΔfliF, ΔflgE and ΔfliC flagellar mutants still produce an empty sheath. Conclusions Our results demonstrate that the flagellum of B. melitensis has the characteristics of the sheathed flagella. Our results also suggest that the flagellar sheath production is not directly linked to the flagellar structure assembly and is not regulated by the FtcR master regulator. PMID:21143933

  12. Porous protective solid phase micro-extractor sheath

    DOEpatents

    Andresen, Brian D.; Randich, Erik

    2005-03-29

    A porous protective sheath for active extraction media used in solid phase microextraction (SPME). The sheath permits exposure of the media to the environment without the necessity of extending a fragile coated fiber from a protective tube or needle. Subsequently, the sheath can pierce and seal with GC-MS septums, allowing direct injection of samples into inlet ports of analytical equipment. Use of the porous protective sheath, within which the active extraction media is contained, mitigates the problems of: 1) fiber breakage while the fiber is extended during sampling, 2) active media coating loss caused by physical contact of the bare fiber with the sampling environment; and 3) coating slough-off during fiber extension and retraction operations caused by rubbing action between the fiber and protective needle or tube.

  13. Solitary fibrous tumor surrounding the carotid sheath.

    PubMed

    Gómez-Oliveira, Guillermo; Alvarez-Flores, Modesto; Arribas-García, Ignacio; Martínez-Gimeno, Carlos

    2010-03-01

    Solitary fibrous tumors (SFTs) are rare spindle cell neoplasms that are mostly found arising from the pleura. Although SFTs recently have been reported in other regions, they are rare in the head and neck and have often been misdiagnosed due to their rarity. SFTs are benign in most cases. Clinically, SFTs usually manifest as well-circumscribed, slow-growing, smooth and painless masses. Symptoms are often minimal, although they may include sore throat, difficulty in swallowing, change of voice or trismus. CT-Scan and MRI are the most sensitive imaging procedures used. The treatment of choice is complete surgical excision of the lesion. Because recurrences have been noted up to 30 years after surgery, long-term follow up is mandatory. In this article, we present a case of a Solitary Fibrous Tumor arising in the parapharyngeal space in a 20-year-old man, involving the carotid sheath, treated by surgical excision with no recurrence after 1 year. The clinical presentation, surgical management and pathological findings are described.

  14. Safety and efficacy of ureteral access sheaths.

    PubMed

    Stern, Joshua M; Yiee, Jenny; Park, Sangtae

    2007-02-01

    The ureteral access sheath (UAS) was introduced as a means of passing a flexible ureteroscope. Although the device was initially lauded for its ability to facilitate ureteroscopic access, passage was difficult and risked ureteral injury, and the UAS fell out of favor until the development of a new generation of devices that was easier to insert. The UAS should be advanced under fluoroscopy over a stiff guidewire, and the surgeon should ensure copious hydration of all inner and outer surfaces. Use of the UAS is purported to improve irrigant flow and visibility. The UAS can induce transient ureteral ischemia and promote an acute inflammatory response, but it also prevents potentially harmful elevations in intrarenal pressure. Unequivocal data are not yet available to suggest that UAS use during ureteroscopy protects or harms the upper urinary tract. The UAS also has the potential to improve stone-free rates by allowing passive egress or active retrieval of fragments. A large prospective study is needed to unequivocally determine if UAS use is superior in terms of stone-free rates. Cost studies reported to favor UAS use, although a formal cost-effectiveness analysis has not been performed. Further study is needed before routine use of the UAS can be recommended.

  15. The impact of frequency mixing on sheath properties: Ion energy distribution and Vdc/Vrf interaction

    NASA Astrophysics Data System (ADS)

    Shannon, Steven; Hoffman, Daniel; Yang, Jang-Gyoo; Paterson, Alex; Holland, John

    2005-05-01

    A dual frequency rf sheath is analyzed using a simple rf sheath model to study the interaction between the two driving rf currents and their effect on sheath parameters. A symmetric rf discharge with defined electron density and dc sheath potential is modeled using a sharp boundary sheath approximation. Three results of this study are reported: (1) reproduction of trends in ion energy distribution functions predicted and measured in previous studies, (2) a frequency-mixing-dependent relationship between the dc sheath potential and applied rf potential, and (3) an additional asymmetry in the ion energy distribution function generated by the intermodulation components resulting from the nonlinear sheath.

  16. Use of an introducer sheath for colonic stent placement.

    PubMed

    De Gregorio, Miguel A; Mainar, Antonio; Tejero, Eloy; Alfonso, Eduardo; Gimeno, María José; Herrera, Marcos

    2002-09-01

    We describe a technical modification of Wallstent implantation for the treatment of malignant rectosigmoid and descending colonic obstructions. The modification is the routine placement of an introducer sheath via the rectum before stent implantation in order to straighten the rectosigmoid region. This device facilitates catheter and guide wire manipulations and obtaining specimen biopsies for histopathological studies. The introducer sheath has been used without complications in 21 consecutive patients.

  17. Plasma sheath effects on ion collection by a pinhole

    NASA Technical Reports Server (NTRS)

    Herr, Joel L.; Snyder, David B.

    1993-01-01

    This work presents tables to assist in the evaluation of pinhole collection effects on spacecraft. These tables summarize results of a computer model which tracks particle trajectories through a simplified electric field in the plasma sheath. A technique is proposed to account for plasma sheath effects in the application of these results and scaling rules are proposed to apply the calculations to specific situations. This model is compared to ion current measurements obtained by another worker, and the agreement is very good.

  18. Sheath fold development around slip surfaces subject to general shear

    NASA Astrophysics Data System (ADS)

    Adamuszek, Marta; Senderak, Barbara; Dabrowski, Marcin

    2016-04-01

    Sheath folds are cone-shaped structures, which typically develop in high-strain shear zones in a variety of geological settings. When observed in the cross-sections perpendicular to the shear direction, sheath folds display characteristic elliptical closed contours. The aspect ratio of the outermost closed contour is commonly used for the classification and quantitative analysis. Alsop and Holdsworth (2006) showed that the outermost aspect ratio observed in the natural sheath folds varies between 1 and 7. Previous work on sheath folds development around slip surfaces focused on simple shear deformation (Reber et al., 2013). The aspect ratio developing under such conditions exhibits values larger than the ones observed in nature. Therefore, we investigate sheath fold development around slip surfaces under general shear conditions, in which a shortening component acts in the direction parallel to the shearing plane and perpendicular to the simple shear direction. In our models, the out-of-plane shortening is accommodated by 1) extension in the shear direction only or by 2) uniform extension perpendicular to the shortening direction (dilation). On one hand, the pure shear deformation leads to a decrease of the aspect ratio of the outermost closed contour of the developed sheath folds. On the other hand, it also modifies the slip surface size and orientation, which promotes development of sheath folds with larger aspect ratios. The numerical simulations show that the latter effect is minor and, for the two tested scenarios, we generate sheath folds with the aspect ratios of the outermost ellipse that favourably compare to the range observed in nature.

  19. Sheath ionization model of beam emissions from large spacecraft

    NASA Technical Reports Server (NTRS)

    Lai, S. T.; Cohen, H. A.; Bhavnani, K. H.; Tautz, M. E.

    1985-01-01

    An analytical model of the charging of a spacecraft emitting electron and ion beams has been applied to the case of large spacecraft. In this model, ionization occurs in the sheath due to the return current. Charge neutralization of spherical space charge flow is examined by solving analytical equations numerically. Parametric studies of potential large spacecraft are performed. As in the case of small spacecraft, the ions created in the sheath by the returning current play a large role in determining spacecraft potential.

  20. Miniature sheathed thermocouples for turbine blade temperature measurement

    NASA Technical Reports Server (NTRS)

    Holanda, R.; Glawe, G. E.; Krause, L. N.

    1974-01-01

    An investigation was made of sheathed thermocouples for turbine blade temperature measurements. Tests were performed on the Chromel-Alumel sheathed thermocouples with both two-wire and single-wire configurations. Sheath diameters ranged from 0.25 to 0.76 mm, and temperatures ranged from 1080 to 1250 K. Both steady-state and thermal cycling tests were performed for times up to 450 hr. Special-order and commercial-grade thermocouples were tested. The tests showed that special-order single-wire sheathed thermocouples can be obtained that are reliable and accurate with diameters as small as 0.25 mm. However, all samples of 0.25-mm-diameter sheathed commercial-grade two-wire and single-wire thermocouples that were tested showed unacceptable drift rates for long-duration engine testing programs. The drift rates were about 1 percent in 10 hr. A thermocouple drift test is recommended in addition to the normal acceptance tests in order to select reliable miniature sheathed thermocouples for turbine blade applications.

  1. Photoelectric sheath formation around small spherical objects in space

    SciTech Connect

    Misra, Shikha Sodha, M. S.; Mishra, S. K.

    2015-04-15

    The formation of a photoelectron sheath around positively charged small (∼cm) spherical objects roaming in near earth space due to the solar radiation (with continuous spectrum) and the solar wind plasma has been investigated. The sheath structure has been derived, taking into account anisotropic photoelectron flux with the Poisson equation, spherical geometry of the object, and half Fermi Dirac distribution of photoelectron velocities. Two cases, viz., when the object is illuminated by (i) isotropic or (ii) unidirectional (parallel beam) radiation, have been analyzed. The analysis predicts a spherically symmetric sheath in case of isotropic illumination, while a symmetry in sheath about a θ=π/4 is seen in case of parallel beam illumination; θ is the angle of incidence which is the angle made by the normal to a surface element with the direction of incidence of solar radiation. The radial and angular profiles of the electric potential and electron density in the photoelectron sheath have been evaluated and illustrated graphically; the dependence of the sheath structure on the solar wind plasma parameters, material properties of the spherical object, and its size have been discussed.

  2. Comment on 'Sheath model for dual-frequency capacitive discharges'

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Cong; Pu, Yi-Kang

    2015-07-01

    Boyle et al (2004 J. Phys. D: Appl. Phys. 37 1451) introduced a sheath model for dual-frequency capacitive discharges. The electron sheath edge position s and the dc potential Φdc in the sheath are obtained with the assumption α/β  >> 1 (where α/β is the ratio of the low-frequency electric field to the high-frequency electric field). However, α/β  ≤  4 is usually found in processing applications. Under this condition, we show that the Boyle et al model gives multiple values for the dc potential Φdc(x) at any given position x in the sheath. For this reason, we introduce a model without the assumption α/β  >> 1. By comparing the results from the two models, it is found that, as the ratio α/β approaches 1, the sheath thickness sm and the sheath dc voltage Vdc obtained with the Boyle et al model are significantly underestimated.

  3. Why ions enter the sheath entrance at supersonic speed?

    NASA Astrophysics Data System (ADS)

    Tang, Xianzhu; Guo, Zehua

    2015-11-01

    In a boundary plasma of a fusion device, the sheath Knudsen number, which is defined as the ratio of the plasma mean-free-path and the plasma Debye length, is much greater than unity, so one anticipates a collisionless sheath, even though the overall boundary plasma in the scrape-off layer is collisional. This is supposed to be the regime for which the Bohm criteria for the ion entry flow at the sheath entrance, v >=cs with cs the sound speed, is usually satisfied at the equal sign. But numerical simulations using first-principles particle-in-cell codes tend to report a supersonic flow. Here we revisit the two-scale and transition layer analysis of the sheath-presheath transition, in tandem with the conventional Bohm criteria analysis, to understand why and how the supersonic sheath entry flow is established at the sheath entrance, which is a few Debye length away from the wall, and its impact on plasma particle and power load at the wall. Works upported by DOE OFES. Work supported by DOE OFES.

  4. The sheath effect on the floating harmonic method

    SciTech Connect

    Lee, Jaewon; Kim, Kyung-Hyun; Chung, Chin-Wook

    2015-12-15

    The floating harmonic method biases sinusoidal voltage to a probe sheath, and as its response, harmonic currents can be obtained. These currents can be used to determine the plasma parameters. However, different shapes of probes have different shapes of sheaths that can affect the diagnostic results. However, no research has been done on the sheath effect on the floating harmonic method. Therefore, we investigate the effect of the sheath during floating harmonic diagnostics by comparing cylindrical and planar probes. While the sinusoidal voltages were applied to a probe, because the sheath oscillated, the time variant ion current and their harmonic currents were added to the electron harmonic currents. In the floating harmonic method, the harmonic currents are composed of only the electron harmonic currents. Therefore, the ion harmonic currents affect the diagnostic results. In particular, the electron temperature obtained by the small probe tip was higher than that of the large probe tip. This effect was exacerbated when the ratio of the probe tip radius to the sheath length was smaller.

  5. Type VI secretion system sheaths as nanoparticles for antigen display

    PubMed Central

    Del Tordello, Elena; Danilchanka, Olga; McCluskey, Andrew J.; Mekalanos, John J.

    2016-01-01

    The bacterial type 6 secretion system (T6SS) is a dynamic apparatus that translocates proteins between cells by a mechanism analogous to phage tail contraction. T6SS sheaths are cytoplasmic tubular structures composed of stable VipA-VipB (named for ClpV-interacting protein A and B) heterodimers. Here, the structure of the VipA/B sheath was exploited to generate immunogenic multivalent particles for vaccine delivery. Sheaths composed of VipB and VipA fused to an antigen of interest were purified from Vibrio cholerae or Escherichia coli and used for immunization. Sheaths displaying heterologous antigens generated better immune responses against the antigen and different IgG subclasses compared with soluble antigen alone. Moreover, antigen-specific antibodies raised against sheaths presenting Neisseria meningitidis factor H binding protein (fHbp) antigen were functional in a serum bactericidal assay. Our results demonstrate that multivalent nanoparticles based on the T6SS sheath represent a versatile scaffold for vaccine applications. PMID:26929342

  6. Ion Velocimetry In Magnetized DC Sheaths

    NASA Astrophysics Data System (ADS)

    Young, Christopher; Lucca Fabris, Andrea; Cappelli, Mark

    2013-09-01

    Particle dynamics near the magnetic cusps in cusped field plasma thrusters are still not well understood; characterizing the ion velocity distribution functions in these regions can help thruster designs maximize electron trapping and minimize erosion of the channel wall. To that end, a robust argon ion velocity sensor is developed using a three-level laser-induced fluorescence (LIF) technique. The 3d4F7 / 2 --> 4p4D5/ 2 0 ArII transition at 668.61 nm is pumped with a 25 mW tunable external cavity diode laser, and fluorescence down to the 4s4P3 / 2 state at 442.72 nm is collected with phase-sensitive detection. The Doppler shift in the acquired signal peak, compared to a stationary reference, gives the ion velocity component parallel to the exciting laser. We demonstrate this LIF scheme by obtaining the argon ion velocity profile through a magnetized DC sheath. The LIF measurement is used to validate a new optogalvanic velocimetry technique in which two lasers (chopped at different frequencies) intersect one another at 90° in the measurement volume. Using a lock-in amplifier, changes observed in the DC discharge current at the sum and difference of the two chopping frequencies may be related back to the mean ion velocity at that point. The authors acknowledge support from the Air Force Office of Scientific Research (AFOSR). CY acknowledges support from the DOE NNSA Stewardship Science Graduate Fellowship under contract DE-FC52-08NA28752.

  7. [The history of the contraceptive sheath].

    PubMed

    Guyotjeannin, C

    1984-06-01

    The condom, effective in preventing both pregnancy and venereal disease, had a limited role until the 19th century, when its use spread through all social strata. The 1st condoms may have been linen sheaths designed to protect against syphilis. A 16th century Neapolitan doctor provided a recipe for an antiseptic preparation to be applied for 4-5 hourrs, but after intercourse had occurred. A physician to Louis XV mentioned the condom in a book published in 1736, and in 1770 the condom was again described without being named. 4 yeears later it was again described and called the condom or English redingote. Later it was mentioned by the Marques de Sade, who alluded to its contraceptive effect. In the early 19th century, condoms made of sheep entrails were mentioned. Descriptions of the preparation of 3 grades of condom, regular, fine, and superfine, were later found. The discovery of the process of vulcanization of rubber in 1839 made possible more solid, marketable, and usable latex condoms. The condom apparently began to be used in the late 17th or early 18th century. Some authors state that it was invented by a Dr. Condom or Conton, a physician or knight in the court of Charls II of England. Othrs suggested that it was named after the city of Condom in Gascony or derived from a foreign word. The antivenereal disease qualities of condoms were described by Casanova and Gustave Flaubert, and other references to them may be found in the literature. Later the contraceptive use of the condom became progressively more common, beginning in the wealthier classes and spreading to the rural and lower classes perhaps by the later 18th century. The diffusion of contraception during the 19th century was cited as the cause of th slow decline in illegitimacy rates starting at the end of the century. The Church condemned the use of condoms for contraception, but the medical profession took a less hostile view due to their health function. At the present time, condoms are widely

  8. Sheath over a finely structured divertor plate

    SciTech Connect

    Cohen, R. H., LLNL

    1998-05-15

    The surface of a divertor plate typically has fine structure. Depending on the material - and the duration of exposure to the plasma, the characteristic size of the surface imperfections may vary over a broad range. In this paper, we consider the case where these structures have scale h that is much smaller than the ion gyroradius {rho}{sub i} but greater than the electron gyroradius {rho}{sub e}. The magnetic field intersects the divertor plate at a shallow angle {alpha}<sheath. We consider only the plasma part of the problem: given the presence of some structure, what are the consequences in terms of the plasma properties in the vicinity of the surface? We are not addressing the issue of what process has caused the appearance of the structure. However, once the plasma part of the problem is solved, on could return to the analysis of the wall erosion problem, based on the solution obtained. For the environment of the divertor region of a medium-size tokamak (plasma density n{approximately}4x10{sup 13} cm{sup -3}, plasma temperature T{approximately}50 eV, the magnetic field strength B{approximately} 2T), one has: {rho}{sub i} {approximately}500 {micro}m (hydrogen), {rho}{sub e}{approximately}10 {micro}m. We, therefore, are going to analyze the scales of imperfections in the range 10 {micro}m

  9. An investigation of tendon sheathing filler migration into concrete

    SciTech Connect

    Naus, D.J.; Oland, C.B.

    1998-03-01

    During some of the inspections at nuclear power plants with prestressed concrete containments, it was observed that the containments has experienced leakage of the tendon sheathing filler (i.e., streaks). The objective of this activity was to provide an indication of the extent of tendon sheathing filler leakage into the concrete and its affects on concrete properties. Literature was reviewed and concrete core samples were obtained from the Trojan Nuclear Plant and tested. The literature primarily addressed effects of crude or lubricating oils that are known to cause concrete damage. However, these materials have significantly different characteristics relative to the materials used as tendon sheathing fillers. Examination and testing of the concrete cores indicated that the appearance of tendon sheathing filler on the concrete surface was due to leakage from the conduits and its subsequent migration through cracks that were present. Migration of the tendon sheathing filler was confined to the cracks and there was no perceptible movement into the concrete. Results of compressive strength testing indicated that the concrete quality was consistent in the containment and that the strength had increased over 40% in 25.4 years relative to the average compressive strength at 28-days age.

  10. Ontogeny of the sheathing leaf base in maize (Zea mays).

    PubMed

    Johnston, Robyn; Leiboff, Samuel; Scanlon, Michael J

    2015-01-01

    Leaves develop from the shoot apical meristem (SAM) via recruitment of leaf founder cells. Unlike eudicots, most monocot leaves display parallel venation and sheathing bases wherein the margins overlap the stem. Here we utilized computed tomography (CT) imaging, localization of PIN-FORMED1 (PIN1) auxin transport proteins, and in situ hybridization of leaf developmental transcripts to analyze the ontogeny of monocot leaf morphology in maize (Zea mays). CT imaging of whole-mounted shoot apices illustrates the plastochron-specific stages during initiation of the basal sheath margins from the tubular disc of insertion (DOI). PIN1 localizations identify basipetal auxin transport in the SAM L1 layer at the site of leaf initiation, a process that continues reiteratively during later recruitment of lateral leaf domains. Refinement of these auxin transport domains results in multiple, parallel provascular strands within the initiating primordium. By contrast, auxin is transported from the L2 toward the L1 at the developing margins of the leaf sheath. Transcripts involved in organ boundary formation and dorsiventral patterning accumulate within the DOI, preceding the outgrowth of the overlapping margins of the sheathing leaf base. We suggest a model wherein sheathing bases and parallel veins are both patterned via the extended recruitment of lateral maize leaf domains from the SAM.

  11. Structure of the Type VI secretion system contractile sheath

    PubMed Central

    Kudryashev, Mikhail; Wang, Ray Yu-Ruei; Brackmann, Maximilian; Scherer, Sebastian; Maier, Timm; Baker, David; DiMaio, Frank; Stahlberg, Henning; Egelman, Edward H.; Basler, Marek

    2015-01-01

    Summary Bacteria use rapid contraction of a long sheath of the Type VI secretion system (T6SS) to deliver effectors into a target cell. Here we present an atomic resolution structure of a native contracted Vibrio cholerae sheath determined by cryo-electron microscopy. The sheath subunits, composed of tightly interacting proteins VipA and VipB, assemble into a six-start helix. The helix is stabilized by a core domain assembled from four β-strands donated by one VipA and two VipB molecules. The fold of inner and middle layers is conserved between T6SS and phage sheaths. However, the structure of the outer layer is distinct and suggests a mechanism of interaction of the bacterial sheath with an accessory ATPase, ClpV, that facilitates multiple rounds of effector delivery. Our results provide a mechanistic insight into assembly of contractile nanomachines that bacteria and phages use to translocate macromolecules across membranes. PMID:25723169

  12. Pulsating fireballs with high-frequency sheath-plasma instabilities

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Gruenwald, J.; Ionita, C.; Schrittwieser, R.

    2011-08-01

    High-frequency instabilities are observed in connection with unstable fireballs. Fireballs are discharge phenomena near positively biased electrodes in discharge plasmas. They are bounded by a double layer whose potential is of order of the ionization potential. Fireballs become unstable when plasma losses and plasma production are not in balance, resulting in periodic fireball pulses. High-frequency instabilities in the range of the electron plasma frequency have been observed. These occur between fireball pulses, hence are not due to electron beam-plasma instabilities since there are no beams without double layers. The instability has been identified as a sheath-plasma instability. Electron inertia creates a phase shift between high-frequency current and electric fields which destabilizes the sheath-plasma resonance. High-frequency signals are observed in the current to the electrode and on probes near the sheath of the electrode. Waveforms and spectra are presented, showing bursty emissions, phase shifts, frequency jumps, beat phenomena between two sheaths, and nonlinear effects such as amplitude clipping. These reveal many interesting properties of sheaths with periodic ionization phenomena.

  13. Structural Conservation of the Myoviridae Phage Tail Sheath Protein Fold

    SciTech Connect

    Aksyuk, Anastasia A.; Kurochkina, Lidia P.; Fokine, Andrei; Forouhar, Farhad; Mesyanzhinov, Vadim V.; Tong, Liang; Rossmann, Michael G.

    2012-02-21

    Bacteriophage phiKZ is a giant phage that infects Pseudomonas aeruginosa, a human pathogen. The phiKZ virion consists of a 1450 {angstrom} diameter icosahedral head and a 2000 {angstrom}-long contractile tail. The structure of the whole virus was previously reported, showing that its tail organization in the extended state is similar to the well-studied Myovirus bacteriophage T4 tail. The crystal structure of a tail sheath protein fragment of phiKZ was determined to 2.4 {angstrom} resolution. Furthermore, crystal structures of two prophage tail sheath proteins were determined to 1.9 and 3.3 {angstrom} resolution. Despite low sequence identity between these proteins, all of these structures have a similar fold. The crystal structure of the phiKZ tail sheath protein has been fitted into cryo-electron-microscopy reconstructions of the extended tail sheath and of a polysheath. The structural rearrangement of the phiKZ tail sheath contraction was found to be similar to that of phage T4.

  14. Particle-in-cell Simulations of the Lunar Photoelectron Sheath

    NASA Astrophysics Data System (ADS)

    Poppe, A. R.; Horanyi, M.

    2009-12-01

    Previous observations have identified a number phenomena on the lunar surface, which are best explained as results of duty plasma processes leading to dust charging, levitation and horizontal transport. These observations include Surveyor images of Horizon Glow (HG), astronaut sketches of dust “streamers” and in-situ measurements made by the Lunar Ejecta and Meteorite (LEAM) experiment. Recent laboratory experiments that approximately reproduced the near surface lunar plasma environment showed that charging can lead to the levitation and transport of dust grains in a tenuous electron sheath. A critical ingredient to the observed phenomena is the presence of a photoelectron sheath, formed when solar ultraviolet radiation causes the lunar regolith to emit electrons. In order to understand the dynamics and underlying physics of dust particles on the surface of the Moon, the lunar photoelectron sheath has been modeled via a 1-dimensional particle-in-cell (PIC) code. In order to validate this code, the results are compared with analytical solutions of the electron density, electric field and sheath thickness for three standard electron velocity distributions. Post-validation, initial simulations have focused on the dependence of the lunar photoelectric sheath on non-standard electron velocity distributions and an incoming solar wind flux. Further additions to the model will include the temporal evolution of the solar UV flux and the presence of dust particles, especially their role as sources and sinks of plasma.

  15. Revisiting the plasma sheath—dust in plasma sheath

    NASA Astrophysics Data System (ADS)

    Das, G. C.; Deka, R.; Bora, M. P.

    2016-04-01

    In this work, we have considered the formation of warm plasma sheath in the vicinity of a wall in a plasma with considerable presence of dust particles. As an example, we have used the parameters relevant in case of plasma sheath formed around surfaces of various solid bodies in space, though the results obtained in this work can be applied to any other physical situation such as laboratory plasma. In the ion-acoustic time scale, we neglect the dust dynamics. The dust particles affect the sheath dynamics by affecting the Poisson equation which determines the plasma potential in the sheath region. It is important to note that our calculations are valid only when the amount of dust particles is not sufficient so as to affect the plasma dynamics in the dust-acoustic time scale, but enough to affect the plasma sheath. We have assumed the current to a dust particle to be balanced throughout the analysis. This makes the grain potential dependent on plasma potential, which is then incorporated into the Poisson equation. The resultant numerical model becomes an initial value problem, which is described by a 1-D integro-differential equation, which is then solved self-consistently by incorporating the change in plasma potential caused by inclusion of the dust potential in the Poisson equation.

  16. Mitigating impact of rectified RF sheath potential on the ELMs

    NASA Astrophysics Data System (ADS)

    Gui, Bin; Xu, Xueqiao; Xia, Tianyang

    2014-10-01

    Here we report on the BOUT++ simulation results for the mitigating impact of rectified RF sheath potential on the peeling-ballooning modes. The limiter and the RF wave antenna are placed at the outer middle plane in the scrape-off-layer (SOL) in shift-circle geometry. The external shear flow is induced by the limiter and the RF wave. Besides this, the sheath boundary conditions are imposed on the perturbed potential and parallel current. From the three-field simulations, it is found that the energy loss is suppressed by the external shear flow in the nonlinear phase. The external shear flow due to the RF wave leads to a broad turbulence spectrum. The wider spectrum leads to a weaker turbulence transport and results in a smaller energy loss. The perturbed electric potential and the parallel current near the sheath region are also suppressed locally due to the sheath boundary condition. Based on this work, this effect of limiter will also be applied in six-field which includes more physics effects. The effect of sheath boundary conditions on the thermal conductivities and heat flux will be studied. This work was performed for USDOE by LLNL under DE-AC52-07NA27344, LLNL LDRD project 12-ERD-022 and the China Natural Science Foundation under Contract No. 10721505. LLNL-ABS-657008.

  17. Measurement of effective sheath width around cutoff probe in low-pressure plasmas

    SciTech Connect

    Kim, D. W.; Oh, W. Y.; You, S. J. Kim, J. H.; Chang, H. Y.

    2014-05-15

    Previous studies indicated that the measurement results of microwave probes can be improved by applying the adequate sheath width to their measurement models, and consequently the sheath width around the microwave probe tips has become very important information for microwave probe diagnostics. In this paper, we propose a method for measuring the argon plasma sheath width around the cutoff probe tips by applying the circuit model to the cutoff probe phase spectrum. The measured sheath width of the cutoff probe was found to be in good agreement with the floated sheath width calculated from the Child-Langmuir sheath law. The physical reasons for a discrepancy between the two measurements are also discussed.

  18. Wave rectification in plasma sheaths surrounding electric field antennas

    NASA Technical Reports Server (NTRS)

    Boehm, M. H.; Carlson, C. W.; Mcfadden, J. P.; Clemmons, J. H.; Ergun, R. E.; Mozer, F. S.

    1994-01-01

    Combined measurements of Langmuir or broadband whistler wave intensity and lower-frequency electric field waveforms, all at 10-microsecond time resolution, were made on several recent sounding rockets in the auroral ionosphere. It is found that Langmuir and whistler waves are partically rectified in the plasma sheaths surrounding the payload and the spheres used as antennas. This sheath rectification occurs whenever the high frequency (HF) potential across the sheath becomes of the same order as the electron temperature or higher, for wave frequencies near or above the ion plasma frequency. This rectification can introduce false low-frequency waves into measurements of electric field spectra when strong high-frequency waves are present. Second harmonic signals are also generated, although at much lower levels. The effect occurs in many different plasma conditions, primarily producing false waves at frequencies that are low enough for the antenna coupling to the plasma to be resistive.

  19. Sheath formation under collisional conditions in presence of dust

    SciTech Connect

    Moulick, R. Goswami, K. S.

    2014-08-15

    Sheath formation is studied for collisional plasma in presence of dust. In common laboratory plasma, the dust acquires negative charges because of high thermal velocity of the electrons. The usual dust charging theory dealing with the issue is that of the Orbit Motion Limited theory. However, the theory does not find its application when the ion neutral collisions are significantly present. An alternate theory exists in literature for collisional dust charging. Collision is modeled by constant mean free path model. The sheath is considered jointly with the bulk of the plasma and a smooth transition of the plasma profiles from the bulk to the sheath is obtained. The various plasma profiles such as the electrostatic force on the grain, the ion drag force along with the dust density, and velocity are shown to vary spatially with increasing ion neutral collision.

  20. Anomalous Capacitive Sheath with Deep Radio Frequency Electric Field Penetration

    SciTech Connect

    Igor D. Kaganovich

    2002-01-18

    A novel nonlinear effect of anomalously deep penetration of an external radio-frequency electric field into a plasma is described. A self-consistent kinetic treatment reveals a transition region between the sheath and the plasma. Because of the electron velocity modulation in the sheath, bunches in the energetic electron density are formed in the transition region adjusted to the sheath. The width of the region is of order V(subscript T)/omega, where V(subscript T) is the electron thermal velocity, and w is frequency of the electric field. The presence of the electric field in the transition region results in a cooling of the energetic electrons and an additional heating of the cold electrons in comparison with the case when the transition region is neglected.

  1. A spine-sheath model for strong-line blazars

    NASA Astrophysics Data System (ADS)

    Sikora, Marek; Rutkowski, Mieszko; Begelman, Mitchell C.

    2016-04-01

    We have developed a quasi-analytical model for the production of radiation in strong-line blazars, assuming a spine-sheath jet structure. The model allows us to study how the spine and sheath spectral components depend on parameters describing the geometrical and physical structure of `the blazar zone'. We show that typical broad-band spectra of strong-line blazars can be reproduced by assuming the magnetization parameter to be of order unity and reconnection to be the dominant dissipation mechanism. Furthermore, we demonstrate that the spine-sheath model can explain why γ-ray variations are often observed to have much larger amplitudes than the corresponding optical variations. The model is also less demanding of jet power than one-zone models, and can reproduce the basic features of extreme γ-ray events.

  2. Micro-Particles as Electrostatic Probes for Plasma Sheath Diagnostic

    SciTech Connect

    Wolter, Matthias; Haass, Moritz; Ockenga, Taalke; Kersten, Holger; Blazec, Joseph; Basner, Ralf

    2008-09-07

    An interesting aspect in the research of complex (dusty) plasmas is the experimental study of the interaction of micro-particles of different sizes with the surrounding plasma for diagnostic purpose. In the plasma micro-disperse particles are negatively charged and confined in the sheath. The particles are trapped by an equilibrium of gravity, electric field force and ion drag force. From the behavior, local electric fields can be determined, e.g. particles are used as electrostatic probes. In combination with additional measurements of the plasma parameters with Langmuir probes and thermal probes as well as by comparison with an analytical sheath model, the structure of the sheath can be described. In the present work we focus on the behavior of micro-particles of different sizes and several plasma parameters e.g. the gas pressure and the rf-power.

  3. Photovoltaic sheathing element with a flexible connector assembly

    DOEpatents

    Langmaid, Joseph A; Keenihan, James R; Mills, Michael E; Lopez, Leonardo C

    2016-07-12

    The present invention is premised upon an assembly including at least a photovoltaic sheathing element capable of being affixed on a building structure, the sheathing element including at least: a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly; at least a first and a second connector assembly disposed on opposing sides of the sheathing element and capable of directly or indirectly electrically connecting the photovoltaic cell assembly to at least two adjoining devices that are affixed to the building structure and wherein at least one of the connector assemblies includes a flexible portion; one or more connector pockets disposed in the body portion the pockets capable of receiving at least a portion of the connector assembly.

  4. Photovoltaic building sheathing element with anti-slide features

    SciTech Connect

    Keenihan, James R.; Langmaid, Joseph A.; Lopez, Leonardo C.

    2015-09-08

    The present invention is premised` upon an assembly that includes at least a photovoltaic building sheathing element capable of being affixed on a building structure, the photovoltaic building sheathing element. The element including a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly; and at feast a first and a second connector assembly capable of directly or indirectly electrically connecting the photovoltaic cell assembly to one or more adjoining devices; wherein the body portion includes one or more geometric features adapted to engage a vertically adjoining device before installation.

  5. Malignant Peripheral Nerve Sheath Tumor -A Rare Malignancy in Mandible.

    PubMed

    Majumdar, Sumit; Kotina, Sreekanth; Mahesh, Nirujogi; Uppala, Divya; Kumar, Singam Praveen

    2016-06-01

    Malignant Peripheral Nerve Sheath Tumor (MPNST) is biologically an aggressive tumor that is usually found in the extremities, trunk and infrequently found in the head and neck area particularly in the jaws, arising from the cells allied with nerve sheath. Mandibular MPNST may either arise from a preexisting neurofibroma or develop de novo. Because of the greater variability from case to case in overall appearance both clinically and histologically, a case of MPNST of the mandible in a 25-year-old female patient is reported. The lesion was excised and immunohistological studies (S-100 & Neuron specific enolase) were conducted to confirm the neural origin.

  6. Malignant Peripheral Nerve Sheath Tumor -A Rare Malignancy in Mandible

    PubMed Central

    Majumdar, Sumit; Kotina, Sreekanth; Uppala, Divya; Kumar, Singam Praveen

    2016-01-01

    Malignant Peripheral Nerve Sheath Tumor (MPNST) is biologically an aggressive tumor that is usually found in the extremities, trunk and infrequently found in the head and neck area particularly in the jaws, arising from the cells allied with nerve sheath. Mandibular MPNST may either arise from a preexisting neurofibroma or develop de novo. Because of the greater variability from case to case in overall appearance both clinically and histologically, a case of MPNST of the mandible in a 25-year-old female patient is reported. The lesion was excised and immunohistological studies (S-100 & Neuron specific enolase) were conducted to confirm the neural origin. PMID:27504425

  7. Bifurcations and chaos in a current-carrying ion sheath

    SciTech Connect

    Komori, A.; Kono, M.; Norimine, T.; Kawai, Y. )

    1992-11-01

    Cascading bifurcations to chaos are investigated experimentally and theoretically in a current-carrying stable plasma. A dc plasma current is required to produce an electron-depleted thick sheath on a grid, which obeys the Child--Langmuir law of space-charge-limited current in a diode. Bifurcation cascade and chaotic behavior are exhibited when an external periodic oscillation is applied to the grid, and are in good agreement for the first time with a theory, which describes ion dynamics in the Child--Langmuir sheath and is represented by the differential equation with three independent variables. A fractal dimension predicted by the theory is verified by the experiment.

  8. Formation of pre-sheath boundary layers in electronegative plasmas

    SciTech Connect

    Vitello, P., LLNL

    1998-05-01

    In electronegative plasmas Coulomb scattering between positive and negative ions can lead to the formation of a pre-sheath boundary layer containing the bulk of the negative ions. The negative ion boundary layer forms when momentum transfer from positive to negative ions dominates the negative ion acceleration from the electric field. This condition is met in Inductively Coupled Plasma reactors that operate at low pressure and high plasma density. Simulations of the GEC reactor for Chlorine and Oxygen chemistries using the INDUCT95 2D model are presented showing the pre-sheath boundary layer structure as a function of applied power and neutral pressure.

  9. Heat pipe design for sheath insulator reactor test

    NASA Astrophysics Data System (ADS)

    Miskolczy, Gabor; Lee, Celia C. M.

    1991-01-01

    A reactor experiment was designed to test the sheath insulator component of the thermionic fuel element (TFE) of a space power reactor. In this fully instrumented reactor test, two gas-controlled sodium heat pipes will be used to control the temperature of the sheath insulator specimens to which an external voltage will be applied. The heat pipes were designed with the aid of a computer program, which predicted performance. A demonstrator heat pipe was built and electrically tested. The test results agreed with the prediction as modeled by the computer program.

  10. Heat pipe design for sheath insulator reactor test

    NASA Astrophysics Data System (ADS)

    Miskolczy, Gabor; Lee, Celia C. M.

    A reactor experiment was designed to test the sheath insulator component of the thermionic fuel element (TFE) of a space power reactor. In this fully instrumented reactor test, two gas-controlled sodium heat pipes will be used to control the temperature of the sheath insulator specimens to which an external voltage will be applied. The heat pipes were designed with the aid of a computer program, which predicted performance. A demonstrator heat pipe was built and electrically tested. The test results agreed with the prediction as modeled by the computer program.

  11. Heat pipe design for sheath insulator reactor test

    SciTech Connect

    Miskolczy, G.; Lee, C.C.M. )

    1991-01-05

    A reactor experiment was designed to test the sheath insulator component of the thermionic fuel element (TFE) of a space power reactor. In this fully instrumented reactor test, two gas-controlled sodium heat pipes will be used to control the temperature of the sheath insulator specimens to which an external voltage will be applied. The heat pipes were designed with the aid of a computer program, which predicted performance. A demonstrator heat pipe was built and electrically tested. The test results agreed with the prediction as modeled by the computer program.

  12. Radiation-induced malignant and atypical peripheral nerve sheath tumors

    SciTech Connect

    Foley, K.M.; Woodruff, J.M.; Ellis, F.T.; Posner, J.B.

    1980-04-01

    The reported peripheral nerve complications of therapeutic irradiation in humans include brachial and lumbar plexus fibrosis and cranial and peripheral nerve atrophy. We have encountered 9 patients with malignant (7) and atypical (2) peripheral nerve tumors occurring in an irradiated site suggesting that such tumors represent another delayed effect of radiation treatment on peripheral nerve. In all instances the radio-theray was within an acceptable radiation dosage, yet 3 patients developed local radiation-induced skin and bony abnormalities. The malignant peripheral nerve sheath tumors developed only in the radiation port. Animal studies support the clinical observation that malignant peripheral nerve sheath tumors can occur as a delayed effect of irradiation.

  13. MOLYBDENUM DISILICIDE MATERIALS FOR GLASS MELTING SENSOR SHEATHS

    SciTech Connect

    J. PETROVIC; R. CASTRO; ET AL

    2001-01-01

    Sensors for measuring the properties of molten glass require protective sensor sheaths in order to shield them from the extremely corrosive molten glass environment. MoSi{sub 2} has been shown to possess excellent corrosion resistance in molten glass, making it a candidate material for advanced sensor sheath applications. MoSi{sub 2}-coated Al{sub 2}O{sub 3} tubes, MoSi{sub 2}-Al{sub 2}O{sub 3} laminate composite tubes, and MoSi{sub 2}-Al{sub 2}O{sub 3} functionally graded composite tubes have been produced by plasma spray-forming techniques for such applications.

  14. Measurement of effective sheath width around the cutoff probe based on electromagnetic simulation

    NASA Astrophysics Data System (ADS)

    Kim, D. W.; You, S. J.; Kim, J. H.; Chang, H. Y.; Yoon, J.-S.; Oh, W. Y.

    2016-05-01

    We inferred the effective sheath width using the cutoff probe and incorporating a full-wave three-dimensional electromagnetic (EM) simulation. The EM simulation reproduced the experimentally obtained plasma-sheath resonance (PSR) on the microwave transmission (S21) spectrum well. The PSR frequency has a one-to-one correspondence with the width of the vacuum layer assumed to be the effective sheath in the EM simulation model. The sheath width was estimated by matching the S21 spectra of the experiment and the EM simulation for different widths of the sheath. We found that the inferred sheath widths quantitatively and qualitatively agree with the sheath width measured by incorporating an equivalent circuit model. These results demonstrate the excellent potential of the cutoff probe for inferring the effective sheath width from its experimental spectrum data.

  15. Deficient Photosystem II in Agranal Bundle Sheath Chloroplasts of C4 Plants

    PubMed Central

    Woo, K. C.; Anderson, Jan M.; Boardman, N. K.; Downton, W. J. S.; Osmond, C. B.; Thorne, S. W.

    1970-01-01

    A method is described for separating mesophyll and bundle sheath chloroplasts from the leaves of C4 plants. The agranal bundle sheath chloroplasts are inactive in the Hill reaction, whereas granal bundle sheath and granal mesophyll chloroplasts exhibit normal photosystem II activity. The agranal bundle sheath chloroplasts are deficient in photosystem II; they lack cytochrome b-559 and the fluorescence bands associated with photosystem II. All the chloroplasts exhibit photosystem I activity. PMID:16591853

  16. Studies of RF sheaths and diagnostics on IShTAR

    NASA Astrophysics Data System (ADS)

    Crombé, K.; Devaux, S.; D'Inca, R.; Faudot, E.; Faugel, H.; Fünfgelder, H.; Heuraux, S.; Jacquot, J.; Louche, F.; Moritz, J.; Ochoukov, R.; Tripsky, M.; Van Eester, D.; Wauters, T.; Noterdaeme, J.-M.

    2015-12-01

    IShTAR (Ion cyclotron Sheath Test ARrangement) is a linear magnetised plasma test facility for RF sheaths studies at the Max-Planck-Institut für Plasmaphysik in Garching. In contrast to a tokamak, a test stand provides more liberty to impose the parameters and gives better access for the instrumentation and antennas. The project will support the development of diagnostic methods for characterising RF sheaths and validate and improve theoretical predictions. The cylindrical vacuum vessel has a diameter of 1 m and is 1.1 m long. The plasma is created by an external cylindrical plasma source equipped with a helical antenna that has been designed to excite the m=1 helicon mode. In inductive mode, plasma densities and electron temperatures have been characterised with a planar Langmuir probe as a function of gas pressure and input RF power. A 2D array of RF compensated Langmuir probes and a spectrometer are planned. A single strap RF antenna has been designed; the plasma-facing surface is aligned to the cylindrical plasma to ease the modelling. The probes will allow direct measurements of plasma density profiles in front of the RF antenna, and thus a detailed study of the density modifications induced by RF sheaths, which influences the coupling. The RF antenna frequency has been chosen to study different plasma wave interactions: the accessible plasma density range includes an evanescent and propagative behaviour of slow or fast waves, and allows the study of the effect of the lower hybrid resonance layer.

  17. Separation system with a sheath-flow supported electrochemical detector

    DOEpatents

    Mathies, Richard A.; Emrich, Charles A.; Singhal, Pankaj; Ertl, Peter

    2008-10-21

    An electrochemical detector including side channels associated with a separation channel of a sample component separation apparatus is provided. The side channels of the detector, in one configuration, provide a sheath-flow for an analyte exiting the separation channel which directs the analyte to the electrically developed electrochemical detector.

  18. Dust-Plasma Sheath in an Oblique Magnetic Field

    SciTech Connect

    Foroutan, G.; Mehdipour, H.

    2008-09-07

    Using numerical simulations of the multi fluid equations the structure of the magnetized sheath near a plasma boundary is studied in the presence of charged dust particles. The dependence of the electron, ion, and dust densities as well as the electrostatic potential, dust charge, and ion normal velocity, on the magnetic field strength and the edge dust number density is investigated.

  19. Modeling a planar sheath in dust-containing plasmas

    SciTech Connect

    Chung, T. H.

    2014-01-15

    One-dimensional fluid model is utilized to describe the sheath at a dust-containing plasma-wall boundary. The model equations are solved on the scale of the electron Debye length. The spatial distributions of electric potential and of the velocities and densities of charged species are calculated in a wide range of control parameters. The dust charge number, electric force, and ion drag force are also investigated. The impacts of Havnes parameter, the electron to ion temperature ratio, the ion collisionality, and the ionization on the spatial distributions of the plasma species and the incident fluxes of the ions to the wall (or to the probe) are investigated. With increase of Havnes parameter, the sheath thickness and the ion flux to the wall are reduced, whereas the ion drift velocity is increased. Enhanced ion thermal motion causes the ion flux to the wall to increase. An increase in ion collisionality with neutrals causes both the sheath thickness and the ion flux to the wall to decrease. With increase of the ionization rate, the sheath thickness is found to decrease and the ion flux collected by a probe increases. The localization of dust particles above the electrode is intensified by the increases in Havnes parameter, the electron to ion temperature ratio, collisionality, and ionization rate.

  20. Effect of secondary electron emission on the plasma sheath

    SciTech Connect

    Langendorf, S. Walker, M.

    2015-03-15

    In this experiment, plasma sheath potential profiles are measured over boron nitride walls in argon plasma and the effect of secondary electron emission is observed. Results are compared to a kinetic model. Plasmas are generated with a number density of 3 × 10{sup 12} m{sup −3} at a pressure of 10{sup −4} Torr-Ar, with a 1%–16% fraction of energetic primary electrons. The sheath potential profile at the surface of each sample is measured with emissive probes. The electron number densities and temperatures are measured in the bulk plasma with a planar Langmuir probe. The plasma is non-Maxwellian, with isotropic and directed energetic electron populations from 50 to 200 eV and hot and cold Maxwellian populations from 3.6 to 6.4 eV and 0.3 to 1.3 eV, respectively. Plasma Debye lengths range from 4 to 7 mm and the ion-neutral mean free path is 0.8 m. Sheath thicknesses range from 20 to 50 mm, with the smaller thickness occurring near the critical secondary electron emission yield of the wall material. Measured floating potentials are within 16% of model predictions. Measured sheath potential profiles agree with model predictions within 5 V (∼1 T{sub e}), and in four out of six cases deviate less than the measurement uncertainty of 1 V.

  1. Rice Sheath Rot: An Emerging Ubiquitous Destructive Disease Complex

    PubMed Central

    Bigirimana, Vincent de P.; Hua, Gia K. H.; Nyamangyoku, Obedi I.; Höfte, Monica

    2015-01-01

    Around one century ago, a rice disease characterized mainly by rotting of sheaths was reported in Taiwan. The causal agent was identified as Acrocylindrium oryzae, later known as Sarocladium oryzae. Since then it has become clear that various other organisms can cause similar disease symptoms, including Fusarium sp. and fluorescent pseudomonads. These organisms have in common that they produce a range of phytotoxins that induce necrosis in plants. The same agents also cause grain discoloration, chaffiness, and sterility and are all seed-transmitted. Rice sheath rot disease symptoms are found in all rice-growing areas of the world. The disease is now getting momentum and is considered as an important emerging rice production threat. The disease can lead to variable yield losses, which can be as high as 85%. This review aims at improving our understanding of the disease etiology of rice sheath rot and mainly deals with the three most reported rice sheath rot pathogens: S. oryzae, the Fusarium fujikuroi complex, and Pseudomonas fuscovaginae. Causal agents, pathogenicity determinants, interactions among the various pathogens, epidemiology, geographical distribution, and control options will be discussed. PMID:26697031

  2. Internal pressure effects in the AIRCO-LCT conductor sheath

    SciTech Connect

    Luton, J.N.; Clinard, J.A.; Lue, J.W.; Gray, W.H.; Summers, L.T.; Kershaw, R.

    1985-01-01

    The large Nb/sub 3/Sn superconducting test coil produced by Westinghouse Electric Corporation for the international Large Coil Task (LCT) utilizes a conductor composed of cabled multifilamentary strands immersed in flowing supercritical helium contained by a square structural sheath made of the high-strength stainless alloy JBX-75. Peak pressures of a few hundred atmospheres are predicted to occur during quench, and measurement of these pressures seems feasible only through penetrations of the sheath wall. Fully processed short lengths of conductor were taken from production ends, fitted with pressure taps and strain gauges, and pressurized with helium gas. Failure, at 1000 atm at liquid nitrogen temperature, was by a catastrophic splitting of the sheath at a corner. Strain measurements and burst pressure agreed with elastic-plastic finite element stress calculations made for the sheath alone. Neither the production seam weld nor the pressure tap penetrations or their fillet welds contributed to the failure, although the finite element calculations show that these areas were also highly stressed, and examination of the failed sample showed that the finite welds were of poor quality. Failure was by tensile overload, with no evidence of fatigue.

  3. 46 CFR 111.05-7 - Armored and metallic sheathed cable.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Armored and metallic sheathed cable. When installed, the metallic armor or sheath must meet the installation requirements of Section 25 of IEEE 45-2002 (incorporated by reference; see 46 CFR 110.10-1). ... 46 Shipping 4 2010-10-01 2010-10-01 false Armored and metallic sheathed cable. 111.05-7...

  4. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that...

  5. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that...

  6. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that...

  7. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that...

  8. 30 CFR 15.32 - Tolerances for weight of explosive, sheath, wrapper, and specific gravity.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., wrapper, and specific gravity. 15.32 Section 15.32 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION... explosive, sheath, wrapper, and specific gravity. (a) The weight of the explosive, the sheath, and the outer.... (c) The specific gravity of the explosive and sheath shall be within ±7.5 percent of that...

  9. Chondroma within the flexor hallucis longus tendon sheath. A case report and literature review.

    PubMed

    Brahms, M A; Fumich, R M

    1978-01-01

    Chondromas in tendon sheaths are a rare entity proviously reported in the flexor sheaths on the hand and possibly the foot. This is the first reported case of condroma of the flexor hallucis longus tendon sheath at the ankle region. A literature review with regard to pathogenesis, classification, and recurrence has been presented.

  10. Evolution of Piled Up Compressions in Modeled CME Sheaths and the Resulting Sheath Structures

    NASA Astrophysics Data System (ADS)

    Das, I.; Opher, M.; Evans, R. M.; Gombosi, T. I.

    2010-12-01

    We study Coronal Mass Ejection (CME) driven shocks and the resulting post shock structures in the lower corona (~ 2-7 Rsun). Two CMEs are erupted by modified Titov-Demoulin (TD) and Gibson-Low (GL) type flux ropes with Space Weather Modeling Framework. We observe a substantial pile up of density compression and a narrow region of plasma depletion layer (PDL) in the simulations. As the CME/flux rope moves and expands in solar wind medium, it pushes the magnetized material laying ahead of it. Hence, the magnetic field lines draping around the CME front are compressed in the sheath just ahead of the CME. These compressed field lines squeeze out the plasma sideways forming PDL in the region. Solar plasma being pushed and displaced from behind, forms a strong piled up compression (PUC) of density downstream of the PDL. Both CMEs have comparable propagation speeds while GL has larger expansion speed than TD due to its higher initial magnetic pressure. We argue that high CME expansion speed along with high solar wind density in the region are responsible for the large PUC found in the lower corona. In case of GL the PUC is much wider although the density compression ratio for both the cases are comparable. Although these simulations artificially initiate out-of-equilibrium CMEs and drive them in an artificial solar wind solution, we predict that PUCs, in general, will be large in the lower corona. This should affect the ion profiles of the accelerated solar energetic particles.

  11. Proteases of Treponema denticola outer sheath and extracellular vesicles.

    PubMed Central

    Rosen, G; Naor, R; Rahamim, E; Yishai, R; Sela, M N

    1995-01-01

    Electron microscopical observations of the oral periodontopathogen Treponema denticola show the presence of extracellular vesicles bound to the bacterial surface or free in the surrounding medium. Extracellular vesicles from T. denticola ATCC 35404, 50 to 100 nm in diameter, were isolated and further characterized. Protein and proteolytic patterns of the vesicles were found to be very similar to those of isolated T. denticola outer sheaths. They were enriched with the major outer sheath polypeptides (molecular sizes, 113 to 234 kDa) and with outer sheath proteases of 91, 153, 173, and 228 kDa. These findings indicate that treponemal outer sheath vesicles contain the necessary adhesins and proteolytic arsenal for adherence to and damage of eucaryotic cells and mammalian matrix proteins. The major outer sheath- and vesicle-associated protease of T. denticola ATCC 35404 was purified and characterized. The purified enzyme had a molecular size of 91 kDa, and it dissociated into three polypeptides of 72, 38, and 35 kDa upon heating in the presence of sodium dodecyl sulfate with or without a reducing agent. The activity of the enzyme could be inhibited by diisopropylfluorophosphate, phenylmethylsulfonyl fluoride, and phenylboronic acid. The value of the second-order rate constant of the protease inactivation by phenylmethylsulfonyl fluoride was 0.48 x 10(4) M(-1) min-1. Inhibition of the enzyme by phenylboronic acid was rapid (< 1 min) and pH dependent. These data strongly suggest that this major surface proteolytic activity belongs to a family of serine proteases. PMID:7558307

  12. Effect of flexor sheath integrity on tendon gliding: a biomechanical and histologic study.

    PubMed

    Peterson, W W; Manske, P R; Kain, C C; Lesker, P A

    1986-01-01

    The effect on tendon gliding of flexor sheath excision versus incision/closure following primary flexor tendon repair was examined biomechanically and histologically in forty-one chickens. There was no significant difference in either the tendon excursion required to fully flex the digit or in the work of flexion (the integration of the forces that resist tendon gliding during excursion) between the sheath excised and sheath closed groups. The results were unaffected by postoperative immobilization or intermittent passive motion. Histologically, it was noted that at 3 weeks the healing tendon was surrounded by a layer of granulation tissue that was nearly identical in both the sheath excised and the sheath closed digits. Of note was the finding that a synovial lining could not be identified in those digits that had previously undergone sheath closure. However, at 6 weeks postoperatively, a new gliding surface could be identified surrounding the tendon in both the sheath excised and the sheath closed digits. This study indicates that closure of the flexor sheath after primary tendon repair does not improve tendon gliding as measured biomechanically. Despite its repair, the flexor sheath does not maintain its synovial characteristics as demonstrated histologically, and a new sheath must subsequently be formed.

  13. The magnetized sheath of a dusty plasma with grains size distribution

    SciTech Connect

    Ou, Jing Gan, Chunyun; Lin, Binbin; Yang, Jinhong

    2015-05-15

    The structure of a plasma sheath in the presence of dust grains size distribution (DGSD) is investigated in the multi-fluid framework. It is shown that effect of the dust grains with different sizes on the sheath structure is a collective behavior. The spatial distributions of electric potential, the electron and ion densities and velocities, and the dust grains surface potential are strongly affected by DGSD. The dynamics of dust grains with different sizes in the sheath depend on not only DGSD but also their radius. By comparison of the sheath structure, it is found that under the same expected value of DGSD condition, the sheath length is longer in the case of lognormal distribution than that in the case of uniform distribution. In two cases of normal and lognormal distributions, the sheath length is almost equal for the small variance of DGSD, and then the difference of sheath length increases gradually with increase in the variance.

  14. The positive ion temperature effect in magnetized electronegative plasma sheath with two species of positive ions

    SciTech Connect

    Shaw, A. K.; Kar, S.; Goswami, K. S.

    2012-10-15

    The properties of a magnetized multi-component (two species of positive ions, negative ions and electrons) plasma sheath with finite positive ion temperature are studied. By using three fluid hydrodynamic model and some dimensionless variables, the ion (both lighter and heavier positive ions, and negative ions) densities, the ion (only for positive ions) velocities, and electric potential inside the sheath are investigated. In addition, the absence and presence of magnetic field and the orientation of magnetic field are considered. It is noticed that, with increase of positive ion temperature, the lighter positive ion density peaks increase only at the sheath edge and shift towards the sheath edge for both absence and presence of magnetic field. For heavier positive ions, in the absence of magnetic field, the density peaks increase at the sheath edge. But in the presence of magnetic field, the density fluctuations increase at the sheath edge. For both the cases, the density peaks shift towards the sheath edge.

  15. Co-electrospinning fabrication and photocatalytic performance of TiO{sub 2}/SiO{sub 2} core/sheath nanofibers with tunable sheath thickness

    SciTech Connect

    Cao, Houbao Du, Pingfan; Song, Lixin; Xiong, Jie Yang, Junjie; Xing, Tonghai; Liu, Xin; Wu, Rongrong; Wang, Minchao; Shao, Xiaoli

    2013-11-15

    Graphical abstract: - Highlights: • The core–sheath TiO{sub 2}/SiO{sub 2} nanofibers were fabricated by co-electrospinning technique. • The catalytic property of nanofibers with different sheath thickness was studied. • The potential methods of improving catalytic efficiency are suggested. - Abstract: In this paper, core/sheath TiO{sub 2}/SiO{sub 2} nanofibers with tunable sheath thickness were directly fabricated via a facile co-electrospinning technique with subsequent calcination at 500 °C. The morphologies and structures of core/sheath TiO{sub 2}/SiO{sub 2} nanofibers were characterized by TGA, FESEM, TEM, FTIR, XPS and BET. It was found that the 1D core/sheath nanofibers are made up of anatase–rutile TiO{sub 2} core and amorphous SiO{sub 2} sheath. The influences of SiO{sub 2} sheath and its thickness on the photoreactivity were evaluated by observing photo-degradation of methylene blue aqueous solution under the irradiation of UV light. Compared with pure TiO{sub 2} nanofibers, the core/sheath TiO{sub 2}/SiO{sub 2} nanofibers performed a better catalytic performance. That was attributed to not only efficient separation of hole–electron pairs resulting from the formation of heterojunction but also larger surface area and surface silanol group which will be useful to provide higher capacity for oxygen adsorption to generate more hydroxyl radicals. And the optimized core/sheath TiO{sub 2}/SiO{sub 2} nanofibers with a sheath thickness of 37 nm exhibited the best photocatalytic performance.

  16. Ultrathin core-sheath fibers for liposome stabilization.

    PubMed

    Li, Zhuang; Kang, Hongliang; Li, Qinmei; Che, Ning; Liu, Zhijing; Li, Pingping; Zhang, Chao; Liu, Ruigang; Huang, Yong

    2014-10-01

    Ultrathin core-sheath fibers with small unilamellar vesicles (SUVs) in the core were prepared by coaxial electrospinning. SUVs/sodium hyaluranate (HA-Na)/water and polyvinylpyrrolidone (PVP)/ethanol solutions were used as core and sheath fluid in electrospinning, respectively. The ultrathin fibers were characterized by scanning and transmission electron microscopy (SEM and TEM) and laser scanning confocal microscopy (LSCM). The SUVs were successfully encapsulated in the core HA-Na matrix of the ultrathin fibers and are in the elliptic shape. The SUVs encapsulated in the core matrix of the ultrathin fibers have an excellent stability. The SUVs embedded in the ultrathin fibers are stable. When the ultrathin fibers were re-dissolved in water after one-month storage at room temperature, the rehydrated SUVs have the similar size and size distribution as the as-prepared SUVs. The liposome-loaded ultrathin fiber mats have the promising applications in wound healing materials.

  17. Spontaneous intraperitoneal rupture of a postpartum rectus sheath haematoma.

    PubMed

    Elmoghrabi, Adel; Mohamed, Mohamed; McCann, Michael; Sachwani-Daswani, Gul

    2016-01-01

    A 35-year-old woman presented to the emergency department (ED) with acute severe abdominal pain at 4 days postpartum. CT of the abdomen revealed a type II rectus sheath haematoma for which she was initially treated conservatively and discharged. A few hours later, she returned to the ED with a picture suggestive of peritonitis. Exploratory laparoscopy was performed and revealed haemoperitoneum and a ruptured area on the posterior rectus sheath. Approximately 2 L of blood was aspirated. Haemostatic control was achieved and closed suction drains secured in position. The patient was discharged in stable condition on postadmission day 6. She continued to follow-up on an outpatient basis and was doing well 3 months postoperatively. PMID:26961567

  18. Moisture Durability with Vapor-Permeable Insulating Sheathing

    SciTech Connect

    Lepage, R.; Lstiburek, J.

    2013-09-01

    Exterior sheathing insulation is an effective strategy in increasing the overall R-value of wall assemblies; other benefits include decreasing the effects of thermal bridging and increasing the moisture durability of the built assembly. Vapor-permeable exterior insulation, such as mineral board or expanded polystyrene foam, are one such product that may be used to achieve these benefits. However,uncertainty exists on the effects of inward driven moisture and the interaction of increased sheathing temperatures on the moisture durability of the edifice. To address these concerns, Building Science Corporation (BSC) conducted a series of hygrothermal models for cities representing a range of different climate zones. This report describes the research project, key research questions, and theprocedures utilized to analyse the problems.

  19. Moisture Durability with Vapor-Permeable Insulating Sheathing

    SciTech Connect

    Lepage, R.; Lstiburek, J.

    2013-09-01

    Exterior sheathing insulation is an effective strategy in increasing the overall R-value of wall assemblies; other benefits include decreasing the effects of thermal bridging and increasing the moisture durability of the built assembly. Vapor-permeable exterior insulation, such as mineral board or expanded polystyrene foam, are one such product that may be used to achieve these benefits. However, uncertainty exists on the effects of inward driven moisture and the interaction of increased sheathing temperatures on the moisture durability of the edifice. To address these concerns, Building Science Corporation (BSC) conducted a series of hygrothermal models for cities representing a range of different climate zones. This report describes the research project, key research questions, and the procedures utilized to analyse the problems.

  20. Ewing sarcoma mimicking a peripheral nerve sheath tumor.

    PubMed

    Mitchell, B D; Fox, B D; Viswanathan, A; Mitchell, A H; Powell, S Z; Cech, D A

    2010-10-01

    We describe the first patient with an extradural, extramedullary Ewing's sarcoma tumor mimicking a nerve sheath tumor with no overt evidence of metastasis. A 28-year-old woman with no past medical history presented with a progressive 3-year history of low back pain and right-sided lower extremity radiculopathy after having failed conservative therapies. MRI of the lumbar spine revealed a right-sided enhancing, dumbbell-shaped lesion at the right neural foramen appearing to originate from the L4 nerve root, suspicious for a peripheral nerve sheath tumor or schwannoma. The patient and findings are discussed in the context of the literature, including an update on the relatively recent diagnostic redesignation of the Ewing's sarcoma family tumors.

  1. Multiple Giant Cell Tumours of Tendon Sheath: A Rare Occurrence

    PubMed Central

    Pathade, Smita Charandas; Kurpad, Ramkumar; Tauheed, Mohammed

    2014-01-01

    Giant Cell Tumours Of Tendon Sheath (GCTTS) are the second most frequent soft tissue tumours affecting the hand with an overall incidence of 1 in 50,000 individuals. These tumours are usually localized and solitary, with multiple GCTTS occurring rarely. Multi-centric origin is considered unusual and very few cases of multiple GCTTS have been reported till date. Here, we report a rare case of a 26-year-old female who presented with multiple painless swellings on palmar aspect of little finger of right hand since six months. Clinical diagnosis of Dupuytren’s contracture was given. Intraoperative examination revealed multiple separate nodules, firmly attached to the flexor tendon synovial sheath. Histopathology showed features of GCTTS. PMID:24596760

  2. Multiple giant cell tumours of tendon sheath: a rare occurrence.

    PubMed

    Pathade, Smita Charandas; Kurpad, Ramkumar; Tauheed, Mohammed

    2014-01-01

    Giant Cell Tumours Of Tendon Sheath (GCTTS) are the second most frequent soft tissue tumours affecting the hand with an overall incidence of 1 in 50,000 individuals. These tumours are usually localized and solitary, with multiple GCTTS occurring rarely. Multi-centric origin is considered unusual and very few cases of multiple GCTTS have been reported till date. Here, we report a rare case of a 26-year-old female who presented with multiple painless swellings on palmar aspect of little finger of right hand since six months. Clinical diagnosis of Dupuytren's contracture was given. Intraoperative examination revealed multiple separate nodules, firmly attached to the flexor tendon synovial sheath. Histopathology showed features of GCTTS.

  3. Giant Cell Tumor of Tendon Sheath in the Knee

    PubMed Central

    Ghnaimat, Malek; Alodat, Mohannad; Aljazazi, Mohammad; Al-Zaben, Raad; Alshwabkah, Jamal

    2016-01-01

    The giant cell tumor of the tendon sheath (GCTTS) is a benign lesion which arises from the synovium of a joint, bursa or tendon sheath, with 85% of the tumors occurring in the fingers and 12% of the tumors located in large joints such as the knee and ankle. The GCTTS is usually monoarticular, slowly proliferative and rarely locally aggressive. This paper reports three cases of this rare lesion in the knee. Patients presented with painful swelling in the anterior knee, MRI showed localized soft tissue masses which were able to be excised. A follow up of the cases showed no recurrences. This case report emphasizes the importance of considering GCTTS in the differential diagnosis of soft tissue swelling and pain in large joints.

  4. Recent sheath physics studies on DIII-D

    NASA Astrophysics Data System (ADS)

    Watkins, J. G.; Labombard, B.; Stangeby, P. C.; Lasnier, C. J.; McLean, A. G.; Nygren, R. E.; Boedo, J. A.; Leonard, A. W.; Rudakov, D. L.

    2015-08-01

    A study to examine some current issues in the physics of the plasma sheath has been recently carried out in DIII-D low power Ohmic plasmas using both flush and domed Langmuir probes, divertor Thomson scattering (DTS), an infrared camera (IRTV), and a new calorimeter triple probe assembly mounted on the Divertor Materials Evaluation System (DIMES). The sheath power transmission factor was found to be consistent with the theoretically predicted value of 7 (±2) for low power plasmas. Using this factor, the three heat flux profiles derived from the LP, DTS, and calorimeter diagnostic measurements agree. Comparison of flush and domed Langmuir probes and divertor Thomson scattering indicates that proper interpretation of flush probe data to get target plate density and temperature is feasible and could potentially yield accurate measurements of target plate conditions where the probes are located.

  5. Studies of RF sheaths and diagnostics on IShTAR

    SciTech Connect

    Crombé, K.; D’Inca, R.; Faugel, H.; Fünfgelder, H.; Jacquot, J.; Ochoukov, R.; Louche, F.; Tripsky, M.; Van Eester, D.; Wauters, T.

    2015-12-10

    IShTAR (Ion cyclotron Sheath Test ARrangement) is a linear magnetised plasma test facility for RF sheaths studies at the Max-Planck-Institut für Plasmaphysik in Garching. In contrast to a tokamak, a test stand provides more liberty to impose the parameters and gives better access for the instrumentation and antennas. The project will support the development of diagnostic methods for characterising RF sheaths and validate and improve theoretical predictions. The cylindrical vacuum vessel has a diameter of 1 m and is 1.1 m long. The plasma is created by an external cylindrical plasma source equipped with a helical antenna that has been designed to excite the m=1 helicon mode. In inductive mode, plasma densities and electron temperatures have been characterised with a planar Langmuir probe as a function of gas pressure and input RF power. A 2D array of RF compensated Langmuir probes and a spectrometer are planned. A single strap RF antenna has been designed; the plasma-facing surface is aligned to the cylindrical plasma to ease the modelling. The probes will allow direct measurements of plasma density profiles in front of the RF antenna, and thus a detailed study of the density modifications induced by RF sheaths, which influences the coupling. The RF antenna frequency has been chosen to study different plasma wave interactions: the accessible plasma density range includes an evanescent and propagative behaviour of slow or fast waves, and allows the study of the effect of the lower hybrid resonance layer.

  6. INTERIOR OF HOG BARN SHOWING MILKING STANCHIONS AND DIAGONAL SHEATHING, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR OF HOG BARN SHOWING MILKING STANCHIONS AND DIAGONAL SHEATHING, LOOKING EAST. (In the 1940s the hog barn was converted to a calf barn to service the growing dairy. After a fire on the property took the Engle’s main barn in 1954, the building was converted into a milking parlor.) - Engle Farm, Barn, 89 South Ebey Road, Coupeville, Island County, WA

  7. Structure of the bipolar plasma sheath generated by SPEAR I

    SciTech Connect

    Katz, I.; Jongeward, G.A.; Davis, V.A.; Mandell, M.J.; Kuharski, R.A.; Lilley, J.R. Jr. ); Raitt, W.J. ); Cooke, D.L. ); Torbert, R.B.; Larson, G.; Rau, D. )

    1989-02-01

    The Space Power Experiment Aboard Rockets I (SPEAR I) biased two 10-cm radius spheres as high as 46,000 V positive with respect to an aluminum rocket body. The experiment measured the steady state current to the spheres and the floating potential of the rocket body. Three-dimensional calculations performed using NASCAP/LEO and POLAR 2.0 show that both ion-collecting and electron-collecting sheaths were formed. The rocket body potential with respect to the ionospheric plasma adjusted to achieve a balance between the electron current collected by the spheres and the secondary electron-enhanced ion current to the rocket body. This current balance was obtained with a large ion-collecting sheath that enveloped most of the electron-collecting sheath and reduced the area for collection of ionospheric electrons. The calculated current is in agreement with the flight measurement of a steady state current of less than 1/10 A. The calculations show that the rocket body was driven thousands of volts negative with respect to the ionospheric plasma. The calculated rocket potential is within the uncertainty of that inferred from ion spectrometer data. The current flowed through the space plasma. There was almost no direct charge transport between the spheres and the rocket body.

  8. Anode Sheath and Double Layer Solutions with Ionization

    NASA Astrophysics Data System (ADS)

    Scheiner, Brett S.; Baalrud, Scott D.

    2014-10-01

    When an electrode in a plasma is biased more positive than the plasma potential it attracts electrons and repels ions forming a region of negative space charge (electron sheath). Ballistic electrons moving towards this anode gain energy equal to the difference in electrostatic potential energy, Δϕ = ϕ (x) -ϕplasma , with a maximum of ϕanode -ϕplasma . When ϕanode is large enough, electrons can gain enough energy to ionize neutral atoms through electron impact ionization. This leads to a layer of increased ion density near the anode, which can exceed the local electron density at large enough anode biases forming a double layer. We model the sheath potential profile using Poisson's equation with a fluid model for the electron density in the case without ionization and formulate an integral equation for the case with ionization where the ion density depends on an integral from ϕ (x) to ϕanode. An analytic form of the sheath electric field is obtained for the case without ionization and we demonstrate that it asymptotically agrees with the Child-Langmuir solution. We numerically obtain double layer solutions when including ionization and show that the potential profile expands beyond that of the Child-Langmuir solution. This work was supported by the Office of Fusion Science at the U.S. Department of Energy under Contract DE-AC04-94SL85000.

  9. TFE sheath insulator in-reactor test design

    NASA Astrophysics Data System (ADS)

    Miskolczy, Gabor; Lee, Celia; Lieb, David

    A description is given of the Instrumental Fast-Reactor Accelerated Component-Sheath Insulator (IFAC-SI) test, which allows a set of selected sheath insulators to be tested in a fast reactor environment while monitoring temperature, voltage, and current for the life of the experiment. Two buffered heat pipes control the temperature of the sheath insulators. Gamma heating provides the input power to the heat pipes, and heat is rejected via radiation to the outer container and a copper conduction fin at the condenser area of each heat pipe. Computer thermal models of the IFAC-SI experiment were developed to investigate the effect of heat input variation, and to determine the effectiveness of the copper fin. These preliminary laboratory tests of the heat pipe and of the heat rejection system were designed for comparison to thermal model results. The results of the low power fin tests are presented. Preliminary experiment results show that the heat rejection is below that predicted by the computer model.

  10. Nonextensivity effect on radio-wave transmission in plasma sheath

    NASA Astrophysics Data System (ADS)

    Mousavi, A.; Esfandiari-Kalejahi, A.; Akbari-Moghanjoughi, M.

    2016-04-01

    In this paper, new theoretical findings on the application of magnetic field in effective transmission of electromagnetic (EM) waves through a plasma sheath around a hypersonic vehicle are reported. The results are obtained by assuming the plasma sheath to consist of nonextensive electrons and thermal ions. The expressions for the electric field and effective collision frequency are derived analytically in the framework of nonextensive statistics. Examination of the reflection, transmission, and absorption coefficients regarding the strength of the ambient magnetic field shows the significance of q-nonextensive parameter effect on these entities. For small values of the magnetic field, the transmission coefficient increases to unity only in the range of - 1 < q < 1 . It is also found that the EM wave transmission through the nonextensive plasma sheath can take place using lower magnetic field strengths in the presence of superthermal electrons compared with that of Maxwellian ones. It is observed that superthermal electrons, with nonextensive parameter, q < 1, play a dominant role in overcoming the radio blackout for hypersonic flights.

  11. Tagging and mapping of rice sheath blight resistant gene.

    PubMed

    Che, K P; Zhan, Q C; Xing, Q H; Wang, Z P; Jin, D M; He, D J; Wang, B

    2003-01-01

    Sheath blight (Rhizoctonia solani Kühn) is one of the severe rice diseases worldwide. In this study, an F(2) population from a cross between "4011" and "Xiangzaoxian19" is used to identify molecular markers linked with the resistant trait. "4011" was a transgenic rice cultivar carrying a resistant gene to sheath blight, while "Xiangzaoxian19" is a highly susceptible one. As a result, five molecular markers, including three RFLP markers converted from RAPD and AFLP markers, and two SSR markers were identified to link with the sheath blight resistant gene. This dominant resistant gene was named as R sb 1 and mapped on rice chromosome 5. The linkage distance between the markers (E-AT:M-CAC(120), E-AT:M-CTA(230), OPN-16(2000), RM164(320) and RM39(300)) and R sb 1 was 1.6 cM, 9.9 cM, 1.6 cM, 15.2 cM and 1.6 cM, respectively.

  12. Unified Model of the rf Plasma Sheath, Part II

    NASA Astrophysics Data System (ADS)

    Riley, Merle

    1996-10-01

    By developing an approximation to the first integral of the Poisson equation, one can obtain solutions for the current-voltage characteristics of an rf plasma sheath that are valid over the whole range of inertial response of the ions to an imposed rf voltage or current. (M.E.Riley, 1995 GEC, abstract QA5, published in Bull. Am. Phys. Soc., 40, 1587 (1995).) The theory has been shown to adequately reproduce current-voltage characteristics of two extreme cases (M.A. Lieberman, IEEE Trans. Plasma Sci. 16, 638 (1988). A. Metze, D.W. Ernie, and H.J.Oskam, J.Appl.Phys., 60, 3081 (1986).) of ion response. In this work I show the effect of different conventions for connecting the sheath model to the bulk plasma. Modifications of the Mach number and a finite electric field at the Bohm point are natural choices. The differences are examined for a sheath in a high density Ar plasma and are found to be insignificant. A theoretical argument favors the electric field modification. *Work performed at Sandia National Labs and supported by US DoE under contract DE-AC04-94AL85000.

  13. Radio-frequency sheath voltages and slow wave electric field spatial structure

    SciTech Connect

    Colas, Laurent Lu, Ling-Feng; Křivská, Alena; Jacquot, Jonathan

    2015-12-10

    We investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the RF parallel electric field emitted by Ion Cyclotron (IC) wave launchers, using a simple model of Slow Wave (SW) evanescence coupled with Direct Current (DC) plasma biasing via sheath boundary conditions in a plasma-filled 2-dimensional (parallel, radial) rectangle. Within a “wide sheaths” asymptotic regime, valid for large-amplitude near RF fields, our model becomes partly linear: the sheath oscillating voltage at open field line boundaries is a linear combination of elementary contributions by every source point of the radiated RF field map. These individual contributions are all the more intense as the SW emission point is toroidally nearer to the sheath walls. A limit formula is given for a source infinitely close to the sheaths. The decay of sheath RF voltages with the sheath/source parallel distance is quantified as a function of two characteristic SW evanescence lengths. Decay lengths are smaller than antenna parallel extensions. The sheath RF voltages at an IC antenna side limiter are therefore mainly sensitive to SW emission near this limiter, as recent observations suggest. Toroidal proximity effects could also explain why sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallel anti-symmetry of the radiated field map. They could also justify current attempts at reducing the RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinity.

  14. Introduction: Evidence-based in vitro fertilization treatment of fresh versus frozen embryo transfer: peeling away the layers of the onion.

    PubMed

    Legro, Richard S

    2016-08-01

    This introduction to this Views and Reviews examines the current evidence for elective fresh versus frozen embryo transfer, delineates complexities that arise as we sift through the available evidence, and speculates on the ideal design of studies to arrive at an evidence-based consensus. Current gaps in the literature, including a lack of reporting on important outcomes such as live birth and maternal and perinatal adverse events, are noted. The difficulty in designing trials is reviewed, including the choice of the time point in the cycle to randomize patients, how to account for all the patients and embyros that are involved in the trial, whether to incorporate prenatal genetic screening, and the best type of study design to address the risk/benefit ratio of these practices. PMID:27421612

  15. Model and particle-in-cell simulation of ion energy distribution in collisionless sheath

    SciTech Connect

    Zhou, Zhuwen; Kong, Bo; Luo, Yuee; Chen, Deliang; Wang, Yuansheng

    2015-06-15

    In this paper, we propose a self-consistent theoretical model, which is described by the ion energy distributions (IEDs) in collisionless sheaths, and the analytical results for different combined dc/radio frequency (rf) capacitive coupled plasma discharge cases, including sheath voltage errors analysis, are compared with the results of numerical simulations using a one-dimensional plane-parallel particle-in-cell (PIC) simulation. The IEDs in collisionless sheaths are performed on combination of dc/rf voltage sources electrodes discharge using argon as the process gas. The incident ions on the grounded electrode are separated, according to their different radio frequencies, and dc voltages on a separated electrode, the IEDs, and widths of energy in sheath and the plasma sheath thickness are discussed. The IEDs, the IED widths, and sheath voltages by the theoretical model are investigated and show good agreement with PIC simulations.

  16. The Relation of Carbon Dioxide Compensation and Chlorenchymatous Vascular Bundle Sheaths in Leaves of Dicots

    PubMed Central

    Crookston, R. Kent; Moss, Dale N.

    1970-01-01

    Low CO2 compensation points have been found to be associated with several unusual characteristics related to photosynthesis. One such characteristic is a prominent, chlorenchymatous vascular bundle sheath in the leaves. It has been suggested that the presence of this sheath in dicotyledons can serve as a means of detecting low CO2-compensating species. We collected 88 dicotyledon species from 22 families reported to have chlorenchymatous sheaths. Of the 88, only three, Tribulus terrestris, L., Boerhaavia paniculata, L. C. Rich, and Trianthema portulacastrum L., had low CO2 compensation points. Cross sections of the leaves of the other species revealed that they did have chlorenchymatous vascular bundle sheaths. However, these sheath cells contained chloroplasts which were not specialized for starch formation as were the bundle sheath chloroplasts of the low CO2-compensating species. Images PMID:16657506

  17. Numerical investigation of the ion temperature effects on magnetized DC plasma sheath

    SciTech Connect

    Khoramabadi, Mansour; Ghomi, Hamid; Shukla, Padma Kant

    2011-04-01

    The properties of a magnetized plasma sheath with finite ion temperature is considered. The effects of the external magnetic field and the ion temperature on the sheath parameters are examined. It is found that by increasing the ion temperature and the magnetic field strength there is an increase in the positive space charge and the ion energy and a decrease in the sheath thickness. Furthermore, the ion temperature has a direct effect on the ion flux toward the wall.

  18. Flexor Tendon Sheath Ganglions: Results of Surgical Excision

    PubMed Central

    Spencer, Edwin E.

    2007-01-01

    The purpose of our study was to review the clinical features and determine the results following surgical excision of a flexor tendon sheath ganglion. A retrospective analysis of 24 consecutive patients (25 ganglions) who underwent excision of a painful flexor tendon sheath ganglion by the same surgeon was performed. The patient’s medical and operative records were reviewed. Each patient was invited to return for an evaluation, which consisted of a clinical interview, completion of a questionnaire, and physical examination. Those patients that were unable to return underwent a detailed telephone interview. Sixteen patients returned for a clinical evaluation, while eight patients underwent a telephone interview. There were 15 women and nine men, with an average age of 43 years (range, 21–68 years). The dominant hand was involved in 15 patients. The long finger was most commonly involved (11 cases). The ganglion arose from the A1 pulley in 13 cases, between the A1 and A2 pulleys in three cases, and from the A2 pulley in nine cases. At an average follow-up of 18.5 months (range, 5–38 months), all of the patients were satisfied with their final result. No patient developed a recurrence and all returned to their previous functional level. There were two minor complications that resolved uneventfully; one patient experienced mild incisional tenderness, while an additional patient experienced transient digital nerve paresthesias. We conclude that surgical excision is a simple, safe, and effective method for treating a painful ganglion of the digital flexor tendon sheath. PMID:18780066

  19. Experimental validation of sheath models at intermediate radio frequencies

    NASA Astrophysics Data System (ADS)

    Sobolewski, Mark

    2013-09-01

    Sheaths in radio-frequency (rf) discharges play a dominant role in determining important properties such as the efficiency of power delivery and utilization, plasma spatial uniformity, and ion energy distributions (IEDs). To obtain high quality predictions for these properties requires sheath models that have been rigorously tested and validated. We have performed such tests in capacitively coupled and rf-biased inductively coupled discharges, for inert as well as reactive gases, over two or more orders of magnitude in frequency, voltage, and plasma density. We measured a complete set of model input and output parameters including rf current and voltage waveforms, rf plasma potential measured by a capacitive probe, electron temperature and ion saturation current measured by Langmuir probe and other techniques, and IEDs measured by mass spectrometers and gridded energy analyzers. Experiments concentrated on the complicated, intermediate-frequency regime of ion dynamics, where the ion transit time is comparable to the rf period and the ion current oscillates strongly during the rf cycle. The first models tested used several simplifying assumptions including fluid treatment of ions, neglect of electron inertia, and the oscillating step approximation for the electron profile. These models were nevertheless able to yield rather accurate predictions for current waveforms, sheath impedance, and the peak energies in IEDs. More recently, the oscillating step has been replaced by an exact solution of Poisson's equation. This results in a modest improvement in the agreement with measured electrical characteristics and IED peak amplitudes. The new model also eliminates the need for arbitrary or nonphysical boundary conditions that arises in step models, replacing them with boundary conditions that can be obtained directly from measurements or theories of the presheath.

  20. Sheath and presheath in ion-ion plasmas via particle-in-cell simulation

    SciTech Connect

    Meige, A.; Leray, G.; Raimbault, J.-L.; Chabert, P.

    2008-02-11

    A full particle-in-cell simulation is developed to investigate electron-free plasmas constituted of positive and negative ions under the influence of a dc bias voltage. It is shown that high-voltage sheaths following the classical Child-law sheaths form within a few microseconds (which corresponds to the ion transit time) after the dc voltage is applied. It is also shown that there exists the equivalent of a Bohm criterion where a presheath accelerates the ions collected at one of the electrodes up to the sound speed before they enter the sheath. From an applied perspective, this leads to smaller sheaths than one would expect.

  1. Calcium ion-mediated assembly and function of glycosylated flagellar sheath of marine magnetotactic bacterium.

    PubMed

    Lefèvre, Christopher T; Santini, Claire-Lise; Bernadac, Alain; Zhang, Wei-Jia; Li, Ying; Wu, Long-Fei

    2010-12-01

    Flagella of some pathogens or marine microbes are sheathed by an apparent extension of the outer cell membrane. Although flagellar sheath has been reported for almost 60 years, little is known about its function and the mechanism of its assembly. Recently, we have observed a novel type of sheath that encloses a flagellar bundle, instead of a single flagellum, in a marine magnetotactic bacterium MO-1. Here, we reported isolation and characterization of the sheath which can be described as a six-start, right-handed helical tubular structure with a diameter of about 100 nm, and a pitch of helix of about 260 nm. By proteomic, microscopic and immunolabelling analyses, we showed that the sheath of MO-1 consists of glycoprotein with an apparent molecular mass > 350 kDa. This protein, named sheath-associated protein (Sap), shows homology with bacterial adhesins and eukaryotic calcium-dependent adherent proteins (cadherin). Most importantly, we showed that calcium ions mediate the assembly of the tubular-shaped sheath and disintegration of the sheath was deleterious for smooth swimming of MO-1 cells. The disintegrated sheath was efficiently reconstituted in vitro by adding calcium ions. Altogether, these results demonstrate a novel bacterial Ca(2+) -dependent surface architecture, which is essential for bacterial swimming. PMID:21091512

  2. Thrombus on Indwelling Central Venous Catheters: The Histopathology of 'Fibrin Sheaths'

    SciTech Connect

    Suojanen, James Norman; Brophy, David Paul; Nasser, Imad

    2000-03-15

    Purpose: Central venous catheters (CVC) may fail for many reasons, though 'fibrin sheaths' blocking catheter ports are usually implicated. We examined the sheaths removed from dialysis catheters to determine their histopathology.Methods: Ten catheter strippings were performed and the removed material was studied grossly and microscopically.Results: The histologic specimens showed thrombus both with and without a proteinaceous sheath.Conclusion: Dialysis catheters fail because of thrombus formation. This can occur in either the absence or presence of a protein coating on the catheter, the so-called 'fibrin sheath.'.

  3. A Cytochemical Study of Extracellular Sheaths Associated with Rigidoporus lignosus during Wood Decay

    PubMed Central

    Nicole, M.; Chamberland, H.; Rioux, D.; Lecours, N.; Rio, B.; Geiger, J. P.; Ouellette, G. B.

    1993-01-01

    An ultrastructural and cytochemical investigation of the development of Rigidoporus lignosus, a white-rot fungus inoculated into wood blocks, was carried out to gain better insight into the structure and role of the extracellular sheaths produced by this fungus during wood degradation. Fungal sheaths had a dense or loose fibrillar appearance and were differentiated from the fungal cell wall early after wood inoculation. Close association between extracellular fibrils and wood cell walls was observed at both early and advanced stages of wood alteration. Fungal sheaths were often seen deep in host cell walls, sometimes enclosing residual wood fragments. Specific gold probes were used to investigate the chemical nature of R. lignosus sheaths. While labeling of chitin, pectin, β-1,4- and β-1,3-glucans, β-glucosides, galactosamine, mannose, sialic acid, RNA, fucose, and fimbrial proteins over fungal sheaths did not succeed, galactose residues and laccase (a fungal phenoloxidase) were found to be present. The positive reaction of sheaths with the PATAg test indicates that polysaccharides such as β-1,6-glucans are important components. Our data suggest that extracellular sheaths produced by R. lignosus during host cell colonization play an important role in wood degradation. Transportation of lignin-degrading enzymes by extracellular fibrils indicates that alteration of plant polymers may occur within fungal sheaths. It is also proposed that R. lignosus sheaths may be involved in recognition mechanisms in fungal cell-wood surface interactions. Images PMID:16349017

  4. The dust motion inside the magnetized sheath - The effect of drag forces

    SciTech Connect

    Pandey, B. P.; Samarian, A.; Vladimirov, S. V.

    2010-08-15

    The isolated charged dust inside the magnetized plasma sheath moves under the influence of the electron and ion drag force and the sheath electrostatic field. The charge on the dust is a function of its radius as well as the value of the ambient sheath potential. It is shown that the charge on the dust determines its trajectory and dust performs the spiraling motion inside the sheath. The location of the turning spiral is determined by the number of negative charge on the dust, which in turn is a function of the dust radius. The back and forth spiraling motion finally causes the dust to move in a small, narrow region of the sheath. For a bigger dust particle, the dust moves closer to the sheath presheath boundary suggesting that the bigger grains, owing to the strong repulsion between the wall and dust, will be unable to travel inside the sheath. Only small, micron-sized grains can travel closer to the wall before repulsion pushes it back toward the plasma-sheath boundary. The temporal behavior of the spiraling dust motion appears like a damped harmonic oscillation, suggesting that the plasma drag force causes dissipation of the electrostatic energy. However, after initial damping, the grain keeps oscillating although with much smaller amplitude. The possible application of the present results to the ongoing sheath experiments is discussed.

  5. The modeling and simulation of plasma sheath effect on GNSS system

    NASA Astrophysics Data System (ADS)

    Song, Zhongguo; Liu, Jiangfan; Du, Yongxing; Xi, Xiaoli

    2015-11-01

    Plasma sheath can potentially degrade global navigation satellite system (GNSS) through signal attenuation as well as phase noise when a hypersonic vehicle reenters the Earth's atmosphere. Modeling and simulation method of GNSS system disturbed by plasma sheath is introduced in this paper by means of electromagnetic wave propagation theory combined with the satellite signal simulation technique. The transmission function of the plasma sheath with stratified model is derived utilizing scattering matrix method. The effects of the plasma sheath on GPS signal reception and positioning performance are examined. Experimental results are presented and discussed, partly supporting the validity of the analytical method proposed.

  6. Development of a core sheath process for production of oxide fibers

    NASA Technical Reports Server (NTRS)

    Freske, S.

    1972-01-01

    Improvements were sought in an oxide fiber of a core sheath configuration intended for structural applications at 2000 F (1093 C). Discontinuities in the core were eliminated by using core materials other than pure alumina, and continuous core sheath fibers were produced. In the case of some core materials, the continuous sections were sufficiently long for applications in short fiber composites. Creep at 2000 F (1093 C) was found to be due, in most cases, to breaks in the core, allowing the glass sheath to creep. Evidence was obtained indicating that a closer match between the thermal expansion coefficient of the sheath and the core would greatly improve the strength.

  7. Lunar electric fields, surface potential and associated plasma sheaths

    NASA Technical Reports Server (NTRS)

    Freeman, J. W.; Ibrahim, M.

    1975-01-01

    A review is given of studies of the electric-field environment of the moon. Surface electric potentials are reported for the dayside and terminator regions, electron and ion densities in the plasma sheath adjacent to each surface-potential regime are evaluated, and the corresponding Debye lengths are estimated. The electric fields, which are approximated by the surface potential over the Debye length, are shown to be at least three orders of magnitude higher than the pervasive solar-wind electric field and to be confined to within a few tens of meters of the lunar surface.

  8. Microparticles deep in the plasma sheath: Coulomb 'explosion'

    SciTech Connect

    Antonova, T.; Du, C.-R.; Ivlev, A. V.; Hou, L.-J.; Thomas, H. M.; Morfill, G. E.; Annaratone, B. M.

    2012-09-15

    A cloud of microparticles was trapped deep in the sheath of a radio-frequency (rf) discharge, very close to the lower (grounded) electrode of the plasma chamber. This was achieved by employing a specifically designed rf-driven segment integrated in the lower electrode, which provided an additional confinement compressing the cloud to a very high density. After switching the rf-driven segment off, the cloud 'exploded' due to mutual interparticle repulsion. By combining a simple theoretical model with different numerical simulation methods, some basic properties of complex plasmas in this highly non-equilibrium regime were determined.

  9. Mechanical Thrombectomy of Iliocaval Thrombosis Using a Protective Expandable Sheath

    SciTech Connect

    Truong, Tri H.; Spuentrup, Elmar; Staatz, Gundula; Wildberger, Joachim E.; Schmitz-Rode, Thomas; Nolte-Ernsting, Claus C.A.; Guenther, Rolf W.; Haage, Patrick

    2004-09-15

    We report a case of successful percutaneous treatment of a subacute ilio-caval venous thrombosis in a 64-year-old female patient by using a novel combination of a rotatory fragmentation device (percutaneous thrombectomy device: PTD) and large wire basket (temporary Guenther basket filter) under temporary caval filter protection using an expandable sheath. Because the patient had multiple myeloma with increased risk for contrast media-induced renal failure, the therapeutic angiographic procedure was performed without iodinated contrast medium. Non-contrast-enhanced MR venography (high-resolution True FISP) confirmed the effective thrombus removal by the percutaneous mechanical thrombectomy procedure.

  10. Dust Particles Alignments and Transitions in a Plasma Sheath

    SciTech Connect

    Stokes, J. D. E.; Samarian, A. A.; Vladimirov, S. V.

    2008-09-07

    The alignments and transitions of two dust particles in a plasma sheath have been investigated. It is shown that the Hamiltonian description of a non-Hamiltonian system can be used to predict qualitative features of possible equilibria in a variety of confinement potentials and can provide useful plasma diagnostics. The results compare favorably with simulation and are used to create new experimental hypotheses. In particular, the symmetry breaking transition of the particles as they leave the horizontal plane admits a Hamiltonian description which is used to elucidate the wake parameter.

  11. Cystic change in primary paediatric optic nerve sheath meningioma.

    PubMed

    Narayan, Daniel; Rajak, Saul; Patel, Sandy; Selva, Dinesh

    2016-08-01

    Primary optic nerve sheath meningiomas (PONSM) are rare in children. Cystic meningiomas are an uncommon subgroup of meningiomas. We report a case of paediatric PONSM managed using observation alone that underwent cystic change and radiological regression. A 5-year-old girl presented with visual impairment and proptosis. Magnetic resonance (MR) imaging demonstrated a PONSM. The patient was left untreated and followed up with regular MR imaging. Repeat imaging at 16 years of age showed the tumour had started to develop cystic change. Repeat imaging at 21 years of age showed the tumour had decreased in size. PMID:27310300

  12. Low-current medium-pressure RF discharge with electron photoemission in the electrode sheath and penetration of the sheath electrons into the discharge column

    SciTech Connect

    Baranov, I. Ya.; Koptev, A. V.

    2007-12-15

    A model is developed for simulating a low-current moderate-pressure RF discharge with allowance for such characteristic discharge properties as the existence of two sheaths near both electrodes throughout the RF field period; the formation of an electron cloud at the sheath boundary that periodically fills the sheath and leaves it, depending on the phase of the applied RF voltage; the production by the sheath electrons of metastable gas particles that interact with the cloud electrons during subsequent field periods, followed by the excitation of metastable states to the emitting levels; the formation of a sheath in a low-current RF discharge due to the overlap of the secondary electron avalanches triggered by electron photoemission from the electrode surface; and the conditions under which the sheath electrons penetrate into the positive column and accumulate there, which makes, thereby making a low-current RF discharge similar to a non-self-sustained discharge. The parameters of the sheath in a low-current RF discharge are determined by the conditions under which the electron photoemission current from the electrode surface in the sheath is self-sustaining and, like the parameters of the positive discharge column, depend on the sort of gas, the gas pressure, the frequency of the applied RF field, and the interelectrode distance. The results of calculating the parameters of the sheath and column of a low-current RF discharge for nitrogen and helium at different pressures, as well as for different field frequencies and interelectrode distances, are presented and are compared with the experimental data.

  13. Intrarenal pressure and irrigation flow with commonly used ureteric access sheaths and instruments

    PubMed Central

    Wright, Anna; Williams, Kevin; Somani, Bhaskar

    2015-01-01

    Introduction Flexible ureterorenoscopy is becoming a first-line treatment for many intrarenal stones. Ureteric access sheaths are commonly used to aid access, stone removal and reduce intrarenal pressure. We evaluated the effects of two commonly used access sheaths on irrigation flow and intrarenal pressure during flexible ureterorenoscopy. We measured the effect of scope instrumentation on flow and pressure. Material and methods We utilized a 10/12F and 12/14F, 35 cm Re-Trace™ access sheath with a FlexX2 scope in a cadaveric porcine kidney. We evaluated the effect of four Nitinol baskets (1.3F, 1.5F, 1.9F, 2.2F), three different 200 µm laser fibres and a hand-held pump. Measurements of irrigation flow and intrarenal pressure were recorded and compared between the different sized access sheaths. Results Flow rates varied widely between access sheaths. Without instrumentation, mean flow was 17 mls/min (10/12F access sheath), versus 33 mls/min (12/14F sheath) (p <0.0001). Increasing basket size produced a gradual reduction in flow and pressure in both access sheaths. Reassuringly, pressures were low overall (<40 cm H2O). Pressures were significantly reduced when using the larger 12/14F sheath, with and without all instrumentations (p <0.0001). Hand-held pump devices have a marked effect on flow and pressure in both sheaths; with pressures rising up to 121 cm H2O with a 10/12F sheath, versus 29 cm H2O (12/14F) (p <0.0001). Conclusions A 12/14F access sheath offered significantly improved irrigation whilst maintaining significantly lower intrarenal pressure, when compared to a 10/12F access sheath in a cadaveric porcine model. Scope instrumentation affects irrigation flow and pressure in both sized sheaths. Furthermore, there should be caution with hand-held pump devices, especially with smaller sized sheaths, as intrarenal pressure can be very high. PMID:26855796

  14. Experimental studies of anode sheath phenomena in a hall thruster.

    SciTech Connect

    Dorf, L. A.; Fisch, N. J.; Raitses, Yevgeny F.

    2004-01-01

    Both electron-repelling (negative anode fall) and electron-attracting (positive anode fall) anode sheaths in a Hall thruster were identified experimentally by performing accurate, non-disturbing near-anode measurements with biased and emissive probes. An interesting new phenomenon revealed by the probe measurements is that the anode fall changes from positive to negative upon removal of the dielectric coating, which appears on the anode surface during the course of Hall thruster operation. Probe measurements in a Hall thruster with three different magnetic field configurations show that an anode fall at the clean anode is a function of the radial magnetic field profile inside the channel. A positive anode fall formation mechanism suggested in this work is that: (1) when the anode front surface is coated with dielectric, a discharge current closes to the anode at the surfaces that remain conductive, (2) a total thermal electron current toward the conductive area is significantly smaller than the discharge current, therefore an additional electron flux needs to be attracted toward the conductive surfaces by the electronattracting sheath that appears at these surfaces.

  15. Measure Guideline: Guidance on Taped Insulating Sheathing Drainage Planes

    SciTech Connect

    Grin, A.; Lstiburek, J.

    2014-09-01

    This guide provides information and recommendations to the following groups: insulation contractors; general contractors; builders; home remodelers; mechanical contractors; and homeowners, as a guide to the work that needs to be done. The order of work completed during home construction and retrofit improvements is important. Health and safety issues must be addressed first and are more important than durability issues. And durability issues are more important than saving energy. Not all techniques can apply to all houses. Special conditions will require special action. Some builders or homeowners will wish to do more than the important but basic retrofit strategies outlined by this guide. The following are best practice and product recommendations from the interviewed contractors and homebuilders who collectively have a vast amount of experience. Three significant items were discussed with the group which are required to make taped insulating sheathing a simple, long term, and durable drainage plane: 1. Horizontal joints should be limited or eliminated wherever possible; 2. Where a horizontal joint exists use superior materials; 3. Frequent installation inspection and regular trade training are required to maintain proper installation. Section 5 of this measure guideline contains the detailed construction procedure for the three recommended methods to effectively seal the joints in exterior insulating sheathing to create a simple, long term, and durable drainage plane.

  16. Kinetic Effects on Plasma Blob Dynamics with Plasma Sheath

    NASA Astrophysics Data System (ADS)

    Hasegawa, Hiroki; Ishiguro, Seiji

    2015-11-01

    Kinetic effects on plasma blob dynamics with plasma sheath have been studied with a three dimensional electrostatic plasma particle simulation code. In the particle simulation, an external magnetic field B is pointing into the z direction (corresponding to the toroidal direction). The strength of ambient magnetic field increases in the positive x direction (corresponding to the counter radial direction), i.e., ∂B / ∂x > 0 . A coherent structure is initially set as a column along the external magnetic field. In our previous study, we investigated kinetic effects on plasma blob dynamics in the system where the periodic boundary condition is applied in the z direction and found that the symmetry breaking in a blob profile occurs by the kinetic effect. In this study, we have applied the particle absorbing boundaries to the ends in the z direction and studied such kinetic effects with the plasma sheath. In the simulation, not only the symmetry breaking shown in the previous study but also other properties which were not found in the periodic boundary case have been observed. Supported by NIFS Collaboration Research programs (NIFS13KNSS038, NIFS15KNSS058, and NIFS14KNXN279) and a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science (KAKENHI 23740411).

  17. Are there internal sheaths in unmagnetized electronegative plasmas?

    NASA Astrophysics Data System (ADS)

    Yip, Chi-Shung; Hershkowitz, Noah

    2009-11-01

    Bounded electronegative plasmas are predicted to have electropositive halos. A recent experiment [1] showed that for a negative ion to electron concentration ratio of α= 0.43 for an Argon-Oxygen plasma, a positive halo was formed as a consequence of negative ions satisfying a Boltzmann relation. When Te/T-> 5+√24 [2] and α> Te/T- [3], the negative ions are predicted to be confined by an internal sheath. Experiments are reported in Ar-SF6 and Ar-Cl2 plasmas aimed at finding the internal sheath by varying the gas concentrations. Experiments are carried out in a hot filament discharge in a multi-dipole chamber. Negative ions concentrations are determined from the phase velocity of C.W. Ion Acoustic Waves. Electron temperature and density are determined using Langmuir probes. Plasma potentials are determined by emissive probes. Argon drift velocities are determined by Laser Induced Flourescence. [1] Ghim, YC and Herskowitz, N, Applied Physics Letters. 94, 15, 151503 (2009) [2] N. Braithwaite and J.E.Allen, J. Physics. D: Appl. Phys 21, 1733 (1988) [3] R. N. Franklin, Plasma Sources Sci. Technol. 11, A31, (2002)

  18. Isolation, Cultural Maintenance, and Taxonomy of a Sheath-Forming Strain of Leptothrix discophora and Characterization of Manganese-Oxidizing Activity Associated with the Sheath

    PubMed Central

    Emerson, David; Ghiorse, William C.

    1992-01-01

    Leptothrix discophora SP-6 was isolated from the outflow reservoir of an artificial iron seep. Its sheathforming phenotype was maintained by slow growth in a mineral salts-vitamin-pyruvate medium under minimal aeration at 20 to 25°C. A sheathless variant, SP-6(sl), was isolated from smooth colonies that appeared on spread plates after rapid growth of SP-6 in well-aerated cultures. SP-6 and SP-6(sl) are closely related but not identical to the previously studied sheathless strain SS-1 (ATCC 43182). Increasing Mn2+ concentrations in the growth medium of SP-6 increased the phase density of the sheath, indicating increased Mn oxide deposition in the sheath. Electron microscopy of cultures grown without added Mn2+ revealed that the sheath consisted of a well-defined inner layer, 30 to 100 nm thick, and a diffuse outer capsular layer of variable thickness. Mn oxides were identified in the sheath by their characteristic ultrastructure, electron density, and X-ray-dispersive energy spectra. In heavily encrusted sheaths, the Mn oxides were evenly distributed in both layers of the sheath. Sheathed cells retained more Mn-oxidizing activity than did sheathless cells after washing with distilled, deionized water; the sheath retained some of its activity after an EDTA-lysozyme-detergent treatment which removed the cells. An ultrafiltration-dialysis procedure significantly increased the recovery of activity from spent media of SP-6 over that reported previously for SS-1 (L.F. Adams and W.C. Ghiorse, J. Bacteriol. 169:1279-1285, 1987). A 108-kDa Mn-oxidizing protein was identified in concentrated spent media of SP-6 and SP-6(sl), and the activity of the concentrates showed stability in detergents comparable to that of SS-1 and patterns of heat inactivation and chemical inhibition similar to those of SS-1. Images PMID:16348826

  19. Isolation, Cultural Maintenance, and Taxonomy of a Sheath-Forming Strain of Leptothrix discophora and Characterization of Manganese-Oxidizing Activity Associated with the Sheath.

    PubMed

    Emerson, D; Ghiorse, W C

    1992-12-01

    Leptothrix discophora SP-6 was isolated from the outflow reservoir of an artificial iron seep. Its sheathforming phenotype was maintained by slow growth in a mineral salts-vitamin-pyruvate medium under minimal aeration at 20 to 25 degrees C. A sheathless variant, SP-6(sl), was isolated from smooth colonies that appeared on spread plates after rapid growth of SP-6 in well-aerated cultures. SP-6 and SP-6(sl) are closely related but not identical to the previously studied sheathless strain SS-1 (ATCC 43182). Increasing Mn concentrations in the growth medium of SP-6 increased the phase density of the sheath, indicating increased Mn oxide deposition in the sheath. Electron microscopy of cultures grown without added Mn revealed that the sheath consisted of a well-defined inner layer, 30 to 100 nm thick, and a diffuse outer capsular layer of variable thickness. Mn oxides were identified in the sheath by their characteristic ultrastructure, electron density, and X-ray-dispersive energy spectra. In heavily encrusted sheaths, the Mn oxides were evenly distributed in both layers of the sheath. Sheathed cells retained more Mn-oxidizing activity than did sheathless cells after washing with distilled, deionized water; the sheath retained some of its activity after an EDTA-lysozyme-detergent treatment which removed the cells. An ultrafiltration-dialysis procedure significantly increased the recovery of activity from spent media of SP-6 over that reported previously for SS-1 (L.F. Adams and W.C. Ghiorse, J. Bacteriol. 169:1279-1285, 1987). A 108-kDa Mn-oxidizing protein was identified in concentrated spent media of SP-6 and SP-6(sl), and the activity of the concentrates showed stability in detergents comparable to that of SS-1 and patterns of heat inactivation and chemical inhibition similar to those of SS-1. PMID:16348826

  20. Effect of two-temperature electrons distribution on an electrostatic plasma sheath

    SciTech Connect

    Ou, Jing; Xiang, Nong; Gan, Chunyun; Yang, Jinhong

    2013-06-15

    A magnetized collisionless plasma sheath containing two-temperature electrons is studied using a one-dimensional model in which the low-temperature electrons are described by Maxwellian distribution (MD) and high-temperature electrons are described by truncated Maxwellian distribution (TMD). Based on the ion wave approach, a modified sheath criterion including effect of TMD caused by high-temperature electrons energy above the sheath potential energy is established theoretically. The model is also used to investigate numerically the sheath structure and energy flux to the wall for plasmas parameters of an open divertor tokamak-like. Our results show that the profiles of the sheath potential, two-temperature electrons and ions densities, high-temperature electrons and ions velocities as well as the energy flux to the wall depend on the high-temperature electrons concentration, temperature, and velocity distribution function associated with sheath potential. In addition, the results obtained in the high-temperature electrons with TMD as well as with MD sheaths are compared for the different sheath potential.

  1. Ion temperature and gas pressure effects on the magnetized sheath dynamics during plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Khoram, M.; Ghomi, H.; Navab Safa, N.

    2016-03-01

    Here, a collisional magnetized plasma with finite ion temperature is considered to examine the effects of the ion temperature and gas pressure on the plasma-sheath dynamics. We use the two-fluid model of plasma-sheath where the nonlinear equations of a dynamic sheath are solved using a full implicit scheme of finite difference method along with some convenient initial and boundary conditions at the plasma center and target. It is found that the ion temperature only has a significant effect on the characteristics of low voltage sheath, while the gas pressure (collision rate) seriously affects the dynamic characteristics of the low and high voltage plasma-sheath. One can see, increasing the ion temperature in low voltage plasma-sheath causes to increase the temporal curve of the ion dose and the ion impact energy on the target, reduces the temporal curve of the sheath width, and has no any effect on the temporal curve of the ion incident angle on the target. However, rising the gas pressure in low and high voltage plasma-sheath reduces all of these temporal curves.

  2. Development and characterization of RiceCAP QTL mapping population for sheath blight resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    RiceCAP is a USDA CSREES funded project that has as one of its main objectives developing genetic markers associated with sheath blight resistance. Sheath blight, caused by Rhizoctonia solani, is an important disease of rice in the southern US. Tolerance to the disease is quantitatively inherited an...

  3. Effect of two-temperature electrons distribution on an electrostatic plasma sheath

    NASA Astrophysics Data System (ADS)

    Ou, Jing; Xiang, Nong; Gan, Chunyun; Yang, Jinhong

    2013-06-01

    A magnetized collisionless plasma sheath containing two-temperature electrons is studied using a one-dimensional model in which the low-temperature electrons are described by Maxwellian distribution (MD) and high-temperature electrons are described by truncated Maxwellian distribution (TMD). Based on the ion wave approach, a modified sheath criterion including effect of TMD caused by high-temperature electrons energy above the sheath potential energy is established theoretically. The model is also used to investigate numerically the sheath structure and energy flux to the wall for plasmas parameters of an open divertor tokamak-like. Our results show that the profiles of the sheath potential, two-temperature electrons and ions densities, high-temperature electrons and ions velocities as well as the energy flux to the wall depend on the high-temperature electrons concentration, temperature, and velocity distribution function associated with sheath potential. In addition, the results obtained in the high-temperature electrons with TMD as well as with MD sheaths are compared for the different sheath potential.

  4. Dusty Plasma Modeling of the Fusion Reactor Sheath Including Collisional-Radiative Effects

    SciTech Connect

    Dezairi, Aouatif; Samir, Mhamed; Eddahby, Mohamed; Saifaoui, Dennoun; Katsonis, Konstantinos; Berenguer, Chloe

    2008-09-07

    The structure and the behavior of the sheath in Tokamak collisional plasmas has been studied. The sheath is modeled taking into account the presence of the dust{sup 2} and the effects of the charged particle collisions and radiative processes. The latter may allow for optical diagnostics of the plasma.

  5. Investigation of the temporal sheath dynamics in the intermediate RF regime

    NASA Astrophysics Data System (ADS)

    Shihab, M.; Elgendy, A. T.; Eremin, D.; Mussenbrock, T.; Brinkmann, R. P.; Korolov, I.; Derzsi, A.; Donko, Z.; Schulze, J.

    2012-10-01

    The nonlinear dynamics of modulated RF plasma boundary sheaths is investigated employing a recently published model termed Ensemble In Spacetime (EST) and Particle In Cell (PIC) model. The EST enables a fast, and kinetically self-consistent simulation of all RF modulated plasma boundary sheaths in all technically relevant discharge regimes, (Shihab et al 2012 J. Phys. D: Appl. Phys. 45 185202). A numerical experiment has been done using PIC approach with an electrically and geometrically symmetric capacitively coupled plasma. Using the resulting ion flux to the sheath and the sheath potential as input parameters, the sheath dynamics is simulated with EST as well. The results of EST are in excellent agreement with the PIC results. A huge reduction in the simulation time is achieved using EST. The ion dynamics in the intermediate regime (i.e., the ion transit time is of the order of the RF period) causes a temporal asymmetry for the sheath dynamics. The memory effects due to the ion inertia is supposed to give rise to a phase difference between the expansion and the contraction phases of the plasma sheath and consequently to a hysteresis of the sheath charge voltage relation.

  6. Allelic analysis of sheath blight resistance with association mapping in rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sheath blight is one of the most devastating diseases world-wide in rice. For the first time, we adopted association mapping to identify quantitative trait loci for sheath blight resistance from the USDA rice mini-core collection. The phenotyping was conducted with a newly developed micro-chamber me...

  7. Confirming QTLs and finding additional loci responsible for resistance to rice sheath blight disease

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rice sheath blight disease (Rhizoctonia solani AG1-1AKühn) is one of the most destructive rice diseases worldwide. Utilization of host resistance is the most economical and environmentally sound strategy in managing sheath blight (ShB). Ten ShB-QTLs were previously mapped in a LJRIL population using...

  8. Ultrastructure and chemical composition of the sheath of Leptothrix discophora SP-6.

    PubMed Central

    Emerson, D; Ghiorse, W C

    1993-01-01

    Light microscopy and transmission electron microscopy of thin sections and metal-shadowed specimens showed that the sheath of Leptothrix discophora SP-6 (ATCC 51168) is a tube-like extracellular polymeric structure consisting of a condensed fabric of 6.5-nm-diameter fibrils underlying a more diffuse outer capsular layer. In thin sections, outer membrane bridges seen to contact the inner sheath layer suggested that the sheath fabric was attached to the outer layer of the gram-negative cell wall. The capsular polymers showed an affinity for cationic colloidal iron and polycationic ferritin, indicating that they carry a negative charge. Cell-free sheaths were isolated by treatment with a mixture of lysozyme, EDTA, and N-lauroylsarcosine (Sarkosyl) or sodium dodecyl sulfate (SDS). Both Sarkosyl- and SDS-isolated sheaths were indistinguishable in microscopic appearance. However, the Mn-oxidizing activity of Sarkosyl-isolated sheaths was more stable than that of SDS-isolated sheaths. The Sarkosyl-isolated sheaths also contained more 2-keto-3-deoxyoctanoic acid and more outer membrane protein than SDS-isolated sheaths. The oven-dried mass of detergent-isolated sheaths represented approximately 9% of the total oven-dried biomass of SP-6 cultures; the oven-dried sheaths contained 38% C, 6.9% N, 6% H, and 2.1% S and approximately 34 to 35% carbohydrate (polysaccharide), 23 to 25% protein, 8% lipid, and 4% inorganic ash. Gas-liquid chromatography showed that the polysaccharide was an approximately 1:1 mixture of uronic acids (glucuronic, galacturonic, and mannuronic acids and at least one other unidentified uronic acid) and an amino sugar (galactosamine). Neutral sugars were not detected. Amino acid analysis showed that sheath proteins were enriched in cysteine (6 mol%). The cysteine residues in the sheath proteins probably provide sulfhydryls for disulfide bonds that play an important role in maintaining the structural integrity of the sheath (D. Emerson and W.C. Ghiorse, J

  9. Ultrastructure and chemical composition of the sheath of Leptothrix discophora SP-6.

    PubMed

    Emerson, D; Ghiorse, W C

    1993-12-01

    Light microscopy and transmission electron microscopy of thin sections and metal-shadowed specimens showed that the sheath of Leptothrix discophora SP-6 (ATCC 51168) is a tube-like extracellular polymeric structure consisting of a condensed fabric of 6.5-nm-diameter fibrils underlying a more diffuse outer capsular layer. In thin sections, outer membrane bridges seen to contact the inner sheath layer suggested that the sheath fabric was attached to the outer layer of the gram-negative cell wall. The capsular polymers showed an affinity for cationic colloidal iron and polycationic ferritin, indicating that they carry a negative charge. Cell-free sheaths were isolated by treatment with a mixture of lysozyme, EDTA, and N-lauroylsarcosine (Sarkosyl) or sodium dodecyl sulfate (SDS). Both Sarkosyl- and SDS-isolated sheaths were indistinguishable in microscopic appearance. However, the Mn-oxidizing activity of Sarkosyl-isolated sheaths was more stable than that of SDS-isolated sheaths. The Sarkosyl-isolated sheaths also contained more 2-keto-3-deoxyoctanoic acid and more outer membrane protein than SDS-isolated sheaths. The oven-dried mass of detergent-isolated sheaths represented approximately 9% of the total oven-dried biomass of SP-6 cultures; the oven-dried sheaths contained 38% C, 6.9% N, 6% H, and 2.1% S and approximately 34 to 35% carbohydrate (polysaccharide), 23 to 25% protein, 8% lipid, and 4% inorganic ash. Gas-liquid chromatography showed that the polysaccharide was an approximately 1:1 mixture of uronic acids (glucuronic, galacturonic, and mannuronic acids and at least one other unidentified uronic acid) and an amino sugar (galactosamine). Neutral sugars were not detected. Amino acid analysis showed that sheath proteins were enriched in cysteine (6 mol%). The cysteine residues in the sheath proteins probably provide sulfhydryls for disulfide bonds that play an important role in maintaining the structural integrity of the sheath (D. Emerson and W.C. Ghiorse, J

  10. The tail sheath structure of bacteriophage T4: a molecular machine for infecting bacteria

    SciTech Connect

    Aksyuk, Anastasia A.; Leiman, Petr G.; Kurochkina, Lidia P.; Shneider, Mikhail M.; Kostyuchenko, Victor A.; Mesyanzhinov, Vadim V.; Rossmann, Michael G.

    2009-07-22

    The contractile tail of bacteriophage T4 is a molecular machine that facilitates very high viral infection efficiency. Its major component is a tail sheath, which contracts during infection to less than half of its initial length. The sheath consists of 138 copies of the tail sheath protein, gene product (gp) 18, which surrounds the central non-contractile tail tube. The contraction of the sheath drives the tail tube through the outer membrane, creating a channel for the viral genome delivery. A crystal structure of about three quarters of gp18 has been determined and was fitted into cryo-electron microscopy reconstructions of the tail sheath before and after contraction. It was shown that during contraction, gp18 subunits slide over each other with no apparent change in their structure.

  11. An investigation of friction-based tendon sheath model appropriate for control purposes

    NASA Astrophysics Data System (ADS)

    Do, T. N.; Tjahjowidodo, T.; Lau, M. W. S.; Phee, S. J.

    2014-01-01

    The tendon sheath mechanism plays an important role in many robotic systems from surgical devices to robot hands. However, many unexpected properties such as nonlinear hysteresis and backlash, which appear in the tendon sheath system, cause major losses in force transmission. This report deals with the characterization of hysteresis phenomenon, which is attributed to the presence of frictional effects on its elements, in a tendon-sheath driven surgical robot. Unlike various approaches presented in the literature that utilized multiple lumped mass elements, this proposed approach models the tendon sheath as one element. A new dynamic friction model that allows accurate description of friction lag and hysteresis behavior in two regimes, i.e. presliding and sliding regimes, for a sheath in arbitrary configuration such as helical and spatial shape has been developed.

  12. Nocturnal ultrasound measurements of optic nerve sheath diameter correlate with intracranial pressure in children with craniosynostosis.

    PubMed

    Driessen, Caroline; van Veelen, Marie-Lise C; Lequin, Maarten; Joosten, Koen F M; Mathijssen, Irene M J

    2012-09-01

    Children with craniosynostosis are at risk for increased intracranial pressure, and additional possibilities to screen for increased intracranial pressure are required. The authors' aim was to use ultrasound measurements of the optic nerve sheath to understand and express the variability of intracranial pressure in syndromic craniosynostosis. Therefore, five pediatric patients with craniosynostosis underwent invasive 24-hour intracranial pressure monitoring and simultaneous optic nerve sheath measurements. In three patients, the intracranial pressure was abnormal, and during the second half of the night, the optic nerve sheath was increased in all three patients. The optic nerve sheath diameter changes during the night and is as dynamic as the intracranial pressure. To the best of their knowledge, the authors are the first to describe a real-time relationship of the optic nerve sheath with increased intracranial pressure in children.

  13. A Sheath Model for Negative Ion Sources Including the Formation of a Virtual Cathode

    SciTech Connect

    McAdams, R.; King, D. B.; Surrey, E.

    2011-09-26

    A one dimensional model of the sheath between the plasma and the wall in a negative ion source has been developed. The plasma consists of positive ions, electrons and negative ions. The model takes into account the emission of negative ions from the wall into the sheath and thus represents the conditions in a caesiated ion source with surface production of negative ions. At high current densities of the emitted negative ions, the sheath is unable to support the transport of all the negative ions to the plasma and a virtual cathode is formed. This model takes this into account and allows the calculation of the transported negative ions across the sheath with the virtual cathode. The model has been extended to allow the linkage between plasma conditions at the sheath edge and the plasma to be made. Comparisons are made between the results of the model and experimental measurements.

  14. THE FINE STRUCTURAL ORGANIZATION OF NERVE FIBERS, SHEATHS, AND GLIAL CELLS IN THE PRAWN, PALAEMONETES VULGARIS

    PubMed Central

    Heuser, John E.; Doggenweiler, Carlos F.

    1966-01-01

    In view of reports that the nerve fibers of the sea prawn conduct impulses more rapidly than other invertebrate nerves and look like myelinated vertebrate nerves in the light microscope, prawn nerve fibers were studied with the electron microscope. Their sheaths are found to have a consistent and unique structure that is unlike vertebrate myelin in four respects: (1) The sheath is composed of 10 to 50 thin (200- to 1000-A) layers or laminae; each lamina is a cellular process that contains cytoplasm and wraps concentrically around the axon. The laminae do not connect to form a spiral; in fact, no cytoplasmic continuity has been demonstrated among them. (2) Nuclei of sheath cells occur only in the innermost lamina of the sheath; thus, they lie between the sheath and the axon rather than outside the sheath as in vertebrate myelinated fibers. (3) In regions in which the structural integrity of the sheath is most prominent, radially oriented stacks of desmosomes are formed between adjacent laminae. (4) An ∼200-A extracellular gap occurs around the axon and between the innermost sheath laminae, but it is separated from surrounding extracellular spaces by gap closure between the outer sheath laminae, as the membranes of adjacent laminae adhere to form external compound membranes (ECM's). Sheaths are interrupted periodically to form nodes, analogous to vertebrate nodes of Ranvier, where a new type of glial cell called the "nodal cell" loosely enmeshes the axon and intermittently forms tight junctions (ECM's) with it. This nodal cell, in turn, forms tight junctions with other glial cells which ramify widely within the cord, suggesting the possibility of functional axon-glia interaction. PMID:5968976

  15. Hertwig's epithelial root sheath cell behavior during initial acellular cementogenesis in rat molars.

    PubMed

    Yamamoto, Tsuneyuki; Yamamoto, Tomomaya; Yamada, Tamaki; Hasegawa, Tomoka; Hongo, Hiromi; Oda, Kimimitsu; Amizuka, Norio

    2014-11-01

    This study was designed to examine developing acellular cementum in rat molars by immunohistochemistry, to elucidate (1) how Hertwig's epithelial root sheath disintegrates and (2) whether epithelial sheath cells transform into cementoblasts through epithelial-mesenchymal transition (EMT). Initial acellular cementogenesis was divided into three developmental stages, which can be seen in three different portions of the root: portion 1, where the epithelial sheath is intact; portion 2, where the epithelial sheath becomes fragmented; and portion 3, where acellular cementogenesis begins. Antibodies against three kinds of matrix proteinases, which degrade epithelial sheath-maintaining factors, including basement membrane and desmosomes, were used to investigate proteolytic activity of the epithelial sheath. Tissue non-specific alkaline phosphatase (TNALP) and keratin were used to investigate EMT. Epithelial sheath cells showed immunoreactivity for all three enzymes at fragmentation, which suggests that epithelial sheath disintegration is enzymatically mediated. Dental follicle cells and cementoblasts showed intense immunoreactivity for TNALP, and from portion 1 through to 3, the reaction extended from the alveolar bone-related zone to the root-related zone. Cells possessing keratin/TNALP double immunoreactivity were virtually absent. Keratin-positive epithelial sheath cells showed negligible immunoreactivity for TNALP, and epithelial cells did not appear to migrate to the dental follicle. Together, these findings suggest that a transition phenotype between epithelial cells and cementoblasts does not exist in the developing dental follicle and hence that epithelial sheath cells do not undergo EMT during initial acellular cementogenesis. In brief, this study supports the notion that cementoblasts derive from the dental follicle. PMID:24859538

  16. Particle trap to sheath contact for a gas-insulated transmission line having a corrugated outer conductor

    DOEpatents

    Fischer, William H.; Cookson, Alan H.; Yoon, Kue H.

    1984-04-10

    A particle trap to outer elongated conductor or sheath contact for gas-insulated transmission lines. The particle trap to outer sheath contact of the invention is applicable to gas-insulated transmission lines having either corrugated or non-corrugated outer sheaths. The contact of the invention includes an electrical contact disposed on a lever arm which in turn is rotatably disposed on the particle trap and biased in a direction to maintain contact between the electrical contact and the outer sheath.

  17. Inoculation and scoring methods for rice sheath blight disease.

    PubMed

    Jia, Yulin; Liu, Guangjie; Park, Dong-Soo; Yang, Yinong

    2013-01-01

    Sheath blight disease of rice caused by the soilborne fungal pathogen Rhizoctonia solani has been a major disease of rice with a serious threat to stable rice production worldwide. Although various cultural practices have been used to manage the disease, it is advantageous and important to screen rice germplasm and identify resistant rice cultivars for more effective disease control. Recent advances in methods for the fungal inoculation and disease evaluation have enabled a better measurement of host resistance by minimizing confounding factors from plant architectures and environmental conditions. This chapter introduces five such methods: (1) detached leaf method; (2) micro-chamber method; (3) mist-chamber method; (4) parafilm sachet method; and (5) aluminum foil method. These methods are useful for screening and evaluating disease reactions of rice germplasm and facilitating the genetic mapping of disease resistance genes.

  18. Primary malignant peripheral nerve sheath tumor at unusual location

    PubMed Central

    Panigrahi, Souvagya; Mishra, Sudhansu Sekhar; Das, Srikant; Dhir, Manmath Kumar

    2013-01-01

    Malignant peripheral nerve sheath tumor (MPNST) is a rare soft tissue sarcoma. Most arise in association with major nerve trunks. Their most common anatomical sites are the proximal portions of the upper and lower extremities and the trunk. MPNSTs have rarely been reported in literature to occur in other unusual body parts. We review all such cases reported till now in terms of site of origin, surgical treatment, adjuvant therapy and outcome and shortly describe our experience with two of these cases. Both of our case presented with lump at unusual sites resembling neurofibroma, one at orbitotemporal area and other in the paraspinal region with characteristic feature of neurofibroma with the exception that both had very short history of progression. They underwent gross total removal of the tumor with adjuvant radiotherapy postoperatively. At 6-month follow-up both are doing well with no evidence of recurrence. PMID:24174807

  19. Electron inertia effects on the planar plasma sheath problem

    SciTech Connect

    Duarte, V. N.; Clemente, R. A.

    2011-04-15

    The steady one-dimensional planar plasma sheath problem, originally considered by Tonks and Langmuir, is revisited. Assuming continuously generated free-falling ions and isothermal electrons and taking into account electron inertia, it is possible to describe the problem in terms of three coupled integro-differential equations that can be numerically integrated. The inclusion of electron inertia in the model allows us to obtain the value of the plasma floating potential as resulting from an electron density discontinuity at the walls, where the electrons attain sound velocity and the electric potential is continuous. Results from numerical computation are presented in terms of plots for densities, electric potential, and particles velocities. Comparison with results from literature, corresponding to electron Maxwell-Boltzmann distribution (neglecting electron inertia), is also shown.

  20. Cerebral malignant nerve sheath tumor, triton tumor variant: case report.

    PubMed

    Bornstein-Quevedo, Leticia; Peralta-Olvera, Fabiola; Marhx-Bracho, Alfonso; Rodríguez-Jurado, Rodolfo; De Leon-Bojorge, Beatriz

    2003-01-01

    A case of a cerebral malignant triton tumor in a 3-year-old boy with a 2-month history of frontal headache and no clinical evidence of neurofibromatosis is reported. The computed tomography (CT) scan showed a large, irregular tumor in the right parietooccipital lobe. A partial surgical resection was performed. Histologically, the tumor was highly cellular and consisted of spindle cells with hyperchromatic and pleomorphic nuclei. Focally, neoplastic cells with rhabdomyoblastic features were found. The immunohistochemical study showed that tumor cells were positive for S-100 protein and CD57, and the rhabdomyoblasts expressed desmin, Myo-D1, and myoglobin. During the postoperative period, a massive intraparenchymal hemorrhage was identified and surgical drainage was performed. The patient worsened and died 10 days after the first surgery. Postmortem study was not authorized. Six cases of cerebral malignant nerve sheath tumor have been described; however, primary intraparenchymal malignant triton tumor has not been previously described.

  1. Iterative methods for plasma sheath calculations: Application to spherical probe

    NASA Technical Reports Server (NTRS)

    Parker, L. W.; Sullivan, E. C.

    1973-01-01

    The computer cost of a Poisson-Vlasov iteration procedure for the numerical solution of a steady-state collisionless plasma-sheath problem depends on: (1) the nature of the chosen iterative algorithm, (2) the position of the outer boundary of the grid, and (3) the nature of the boundary condition applied to simulate a condition at infinity (as in three-dimensional probe or satellite-wake problems). Two iterative algorithms, in conjunction with three types of boundary conditions, are analyzed theoretically and applied to the computation of current-voltage characteristics of a spherical electrostatic probe. The first algorithm was commonly used by physicists, and its computer costs depend primarily on the boundary conditions and are only slightly affected by the mesh interval. The second algorithm is not commonly used, and its costs depend primarily on the mesh interval and slightly on the boundary conditions.

  2. Precession of cylindrical dust particles in the plasma sheath

    SciTech Connect

    Banu, N.; Ticoş, C. M.

    2015-10-15

    The vertical precession of cylindrical dust particles levitated in the sheath of an rf plasma is experimentally investigated. Typically, the dust particles have two equilibrium positions depending on the orientation of their longitudinal axis: horizontal and vertical. A transition between these two states is induced by rapidly increasing the neutral gas pressure in the plasma chamber. During this transition, the cylindrical dust particles make an angle with the horizontal and rotate about their center of mass. The rotation speed increases as the dust rods aligned with the vertical axis. All dust particles will eventually end up in the vertical state while spinning fast about their longitudinal axis. Dust-dust interaction and the attracting ion wakes are possible mechanisms for inducing the observed dust precession.

  3. Plasma sheath in the presences of non-Maxwellian energetic electrons and secondary emission electrons

    NASA Astrophysics Data System (ADS)

    Ou, Jing; Lin, Binbin; Zhao, Xiaoyun; Yang, Youlei

    2016-07-01

    The formation of a sheath in front of a carbon or tungsten material plane immersed in a plasma containing non-Maxwellian energetic electrons and secondary emission electrons is studied using a 1D model. In the model, energetic electrons are described by the electron energy distribution function (EEDF) and secondary electron emission (SEE) is produced by the electrons impinging on the wall. It is found that SEE coefficient depends on not only the sheath potential but also the EEDF profile of energetic electrons when a non-Maxwellian energetic electron component is present. The energetic electrons and associated secondary emission electrons can strongly modify ion velocity at sheath edge, floating potential and I–V probe characteristic. Due to the interdependence between SEE coefficient originating from the impact of non-Maxwellian energetic electrons on the wall and the sheath potential, with the increase in the energy of energetic electrons, a sudden jump phenomenon can be found in the profiles of SEE coefficient and other quantities such as floating potential and ion velocity at the sheath edge for tungsten wall, while for carbon wall they are the continuous variation. To begin with, the energetic electron component does not dominate the sheath, and I–V probe characteristic depends on both the EEDF profile of energetic electrons and material properties. Once the energetic electron component dominates the sheath, the analysis of I–V probe characteristic will yield the energy of energetic electrons.

  4. Sheath structure in plasmas with nonextensively distributed electrons and thermal ions

    SciTech Connect

    Hatami, M. M.

    2015-02-15

    Sheath region of an electropositive plasma consisting of q-nonextensive electrons and singly charged positive ions with finite temperature is modeled. Using Sagdeev's pseudo potential technique to derive the modified sheath formation criterion, it is shown that the velocity of ions at the sheath edge is directly proportional to the ion temperatures and inversely proportional to the degree of nonextensivity of electrons (q-parameter). Using the modified Bohm criterion, effect of degree of nonextensivity of electrons and temperature of positive ions on the characteristics of the sheath region are investigated numerically. It is shown that an increase in the ion temperature gives rise to an increase in the electrostatic potential and the velocity of ions in the sheath regardless of the value of q. Furthermore, it is seen that the sheath width and the density distribution of the charged particles decrease by increasing the temperature of positive ions. In addition, it is found that the positive ion temperature is less effective on the sheath structure for higher values of the q-parameter. Finally, the results obtained for a thermal plasma with nonextensively distributed electrons are compared with the results of a cold plasma with nonextensive electrons and an extensive (Maxwellian) plasma with thermal ions.

  5. Hertwig’s Epithelial Root Sheath Fate during Initial Cellular Cementogenesis in Rat Molars

    PubMed Central

    Yamamoto, Tsuneyuki; Yamada, Tamaki; Yamamoto, Tomomaya; Hasegawa, Tomoka; Hongo, Hiromi; Oda, Kimimitsu; Amizuka, Norio

    2015-01-01

    To elucidate the fate of the epithelial root sheath during initial cellular cementogenesis, we examined developing maxillary first molars of rats by immunohistochemistry for keratin, vimentin, and tissue non-specific alkaline phosphatase (TNALP) and by TdT-mediated dUTP nick end labeling (TUNEL). The advancing root end was divided into three sections, which follow three distinct stages of initial cellular cementogenesis: section 1, where the epithelial sheath is intact; section 2, where the epithelial sheath becomes fragmented; and section 3, where initial cellular cementogenesis begins. After fragmentation of the epithelial sheath, many keratin-positive epithelial sheath cells were embedded in the rapidly growing cellular cementum. A few unembedded epithelial cells located on the cementum surface. Dental follicle cells, precementoblasts, and cementoblasts showed immunoreactivity for vimentin and TNALP. In all three sections, there were virtually no cells possessing double immunoreactivity for vimentin-keratin or TNALP-keratin and only embedded epithelial cells showed TUNEL reactivity. Taken together, these findings suggest that: (1) epithelial sheath cells divide into two groups; one group is embedded in the cementum and thereafter dies by apoptosis, and the other survives on the cementum surface as epithelial cell rests of Malassez; and (2) epithelial sheath cells do not undergo epithelial-mesenchymal transition during initial cellular cementogenesis. PMID:26160988

  6. Considerations in the surgical use of the flexor sheath and pulley system.

    PubMed

    Lowrie, A G; Lees, V C

    2014-01-01

    The use of the digital flexor sheath to reconstruct damaged structures in the fingers is an intriguing but under-investigated subject. The sheath is anchored firmly to the phalanges and palmar plates and has well-vascularized outer and synovial inner layers. The middle layer is strong and fibrous and not all of it is required for its main biomechanical function of maintaining the moment arm of the flexor tendons. These characteristics have led to several descriptions of different reconstructive uses. In sheath reconstruction, flaps can be used to repair damaged A2 and A4 pulleys. As an anchor, the sheath is useful for tenodeses and tendon transfers. It has been used in the correction of ulnar claw and swan neck deformities. In ligament reconstruction, the A1 pulley has been used to reconstruct the transverse intermetacarpal ligament in cleft hand and ray amputations. The sheath has also been used to cover tendon repairs and periosteal defects with the aim of decreasing adhesions. There is potential for further use of the flexor sheath in reconstructive surgery. The digital flexor sheath can be used to restore various finger functions providing its physiological roles are recognized and preserved. This review considers the different techniques described and their potential uses. PMID:24170491

  7. Electrospun biphasic drug release polyvinylpyrrolidone/ethyl cellulose core/sheath nanofibers.

    PubMed

    Yu, D G; Wang, X; Li, X Y; Chian, W; Li, Y; Liao, Y Z

    2013-03-01

    The capability of core/sheath nanofibers prepared using coaxial electrospinning to provide adjustable biphasic drug release was investigated. Using ketoprofen (KET) as the model drug, polyvinylpyrrolidone as the sheath polymer, and ethyl cellulose as the core matrix, the coaxial process could be conducted smoothly and continuously without spinneret clogging. Scanning electron microscopy and transmission electron microscopy revealed linear nanofibers with homogeneous and clear core/sheath structures. Differential scanning calorimetry and X-ray diffraction verified that the core/sheath nanofibers were nanocomposites, with the drug present in the polymer matrix in an amorphous state. Attenuated total reflectance-Fourier transform infrared spectra demonstrated that the sheath polymer and core matrix were compatible with KET owing to hydrogen bonding. In vitro dissolution tests showed that the core/sheath nanofibers could provide typical biphasic drug release profiles consisting of an immediate and sustained release. The amount of drug released in the first phase was tailored by adjusting the sheath flow rate, and the remaining drug released in the second phase was controlled by a typical diffusion mechanism. The present study shows a simple and useful approach for the systematic design and fabrication of novel biomaterials with structural characteristics for providing complicated and programmed drug release profiles using coaxial electrospinning.

  8. Effect of electron reflection on magnetized plasma sheath in an oblique magnetic field

    SciTech Connect

    Wang, Ting-Ting; Ma, J. X. Wei, Zi-An

    2015-09-15

    Magnetized plasma sheaths in an oblique magnetic field were extensively investigated by conventionally assuming Boltzmann relation for electron density. This article presents the study of the magnetized sheath without using the Boltzmann relation but by considering the electron reflection along the magnetic field lines caused by the negative sheath potential. A generalized Bohm criterion is analytically derived, and sheath profiles are numerically obtained, which are compared with the results of the conventional model. The results show that the ion Mach number at the sheath edge normal to the wall has a strong dependence on the wall potential, which differs significantly from the conventional model in which the Mach number is independent of the wall potential. The floating wall potential is lower in the present model than that in the conventional model. Furthermore, the sheath profiles are appreciably narrower in the present model when the wall bias is low, but approach the result of the conventional model when the wall bias is high. The sheath thickness decreases with the increase of ion-to-electron temperature ratio and magnetic field strength but has a complex relationship with the angle of the magnetic field.

  9. Soil sheaths, photosynthate distribution to roots, and rhizosphere water relations for Opuntia ficus-indica

    SciTech Connect

    Huang, B.; North, G.B.; Nobel, P.S. )

    1993-09-01

    Soil sheaths incorporating aggregated soil particles surround young roots of many species, but the effects of such sheaths on water movement between roots and the soil are largely unknown. The quantity and location of root exudates associated with soil sheath along the entire length of its young roots, except within 1.4 cm of the tip. The soil sheaths, which average 0.7 mm in thickness, were composed of soil particles and root hairs, both of which were covered with exuded mucilaginous material. As determined with a [sup 14]C pulse-labeling technique, 2% of newly fixed [sup 14]C-photosynthate was translocated into the roots at 3d, 6% at 9 d, and 8% at 15 d after labeling. The fraction of insoluble [sup 14]C in the roots increased twofold from 3 d to 15 d. Over the same time period, 6%-9% of the [sup 14]C translocated to the roots was exuded into the soil. The soluble [sup 14]C compounds exuded into the soil were greater in the 3-cm segment at the root tip than elsewhere along the root, whereas mucilage was exuded relatively uniformly along roots 15 cm in length. The volumetric efflux of water increase for both sheathed and unsheathed roots as the soil water potential decreased form -0.1 MPa to -1.0 MPa. The efflux rate was greater for unsheathed roots than for sheathed roots, which were more turgid and had a higher water potential, especially at lower soil water potentials. During drying, soil particles in the sheaths aggregate more tightly, making the sheaths less permeable to water and possibly creating air gaps. The soil sheaths of O. ficus-indica thus reduce water loss from the roots to a drying soil. 34 refs., 6 figs., 1 tab.

  10. The Effect of Polarization on the Stability of Current Sheaths in Space Plasma

    NASA Astrophysics Data System (ADS)

    Lyahov, Vladimir; Neshchadim, Vladimir

    2013-04-01

    The procedure of study of the stability of current sheath taking into account the effect of plasma polarization is proposed. The kinetic equation with self-consistent electromagnetic field for perturbation of distribution function is solved. On the basis of this solution the tensor of dielectric permeability of nonelectroneutral sharply-irregular current sheath plasma is calculated and the dispersion equation to study the possible instability modes of this sheath is obtained. Instability of the current sheath of magnetospheric tail with respect to the tearing-perturbations as well as influence of the effect of plasma polarization on the development of tearing instability is investigated. As a result of application of the offered procedure the existence of low-frequency tearing-like modes which essentially differ from the formerly known tiring-perturbations is revealed even for the case of an electroneutral current sheath. The increment of growth of those modes is positive within very wide interval of wave lengths and attains much bigger quantities than it was supposed earlier for the tearing-instability. Due to this polarization effect, the area of existence of those low-frequency tearing-like modes is displaced from the area of strong stationary electric field more close to the magnitoneutral (and electroneutral) plane at the center of symmetry of the current sheath. The problem of structural stability of the nonelectroneutral current sheath is explored. The equilibrium model represents a system of four connected non-linear first-order differential equations and hence it should manifest the property of structural instability - sensitivity to infinitesimal changes of the parameters and initial conditions. The solution for such current sheath is realized only in some areas of 7-dimensional space of model parameters. The phase volume of those areas is small in comparison with the entire phase volume in the interval on which the parameters are defined. The above is

  11. Dust charging and charge fluctuations in a weakly collisional radio-frequency sheath at low pressure

    SciTech Connect

    Piel, Alexander Schmidt, Christian

    2015-05-15

    Models for the charging of dust particles in the bulk plasma and in the sheath region are discussed. A new model is proposed that describes collision-enhanced ion currents in the sheath. The collisions result in a substantial reduction of the negative charge of the dust. Experimental data for the dust charge in the sheath can be described by this model when a Bi-Maxwellian electron distribution is taken into account. Expressions for the dust charging rate for all considered models are presented and their influence on the rise of the kinetic dust temperature is discussed.

  12. Fat drops in wrist tendon sheaths on MRI in conjunction with a radius fracture.

    PubMed

    Verhagen, Martijn V; Chesaru, Ileana

    2016-08-01

    A case is presented in which fat drops are seen on MRI inside extensor compartment 2 and 3, in conjunction with a radius fracture. The occurrence of traumatic tendon sheath fat-fluid levels has been sparsely reported on CT and MR imaging. This case is the first report of post-traumatic tendon sheath fat drops. Although the clinical relevance of tendon sheath fat drops seems to be limited, it is important to detect and correctly diagnose these fat drops in order to provide an accurate and complete radiologic report. PMID:27170371

  13. Excellent response of malignant peripheral nerve sheath tumour of retroperitoneum to radiation therapy

    PubMed Central

    Akhavan, Ali; Binesh, Fariba; Ghannadi, Fazlollah; Navabii, Hossein

    2012-01-01

    Malignant peripheral nerve sheath tumours are high-grade sarcomas originating from Schwann cells or nerve sheath cells. Most of these tumours are associated with major nerves of the body wall and extremities. The lower extremity and the retroperitoneum are the most common sites. Surgery is the cornerstone of treatment, however, radiation therapy is usually used as an adjuvant treatment. In this paper we present a 57-year-old Iranian woman with malignant peripheral nerve sheath tumour of retroperitoneum who was operated subtotally and then underwent radiation therapy which led to disappearance of all gross residual disease. PMID:23257269

  14. Dissociation and Re-Aggregation of Multicell-Ensheathed Fragments Responsible for Rapid Production of Massive Clumps of Leptothrix Sheaths.

    PubMed

    Kunoh, Tatsuki; Nagaoka, Noriyuki; McFarlane, Ian R; Tamura, Katsunori; El-Naggar, Mohamed Y; Kunoh, Hitoshi; Takada, Jun

    2016-01-01

    Species of the Fe/Mn-oxidizing bacteria Leptothrix produce tremendous amounts of microtubular, Fe/Mn-encrusted sheaths within a few days in outwells of groundwater that can rapidly clog water systems. To understand this mode of rapid sheath production and define the timescales involved, behaviors of sheath-forming Leptothrix sp. strain OUMS1 were examined using time-lapse video at the initial stage of sheath formation. OUMS1 formed clumps of tangled sheaths. Electron microscopy confirmed the presence of a thin layer of bacterial exopolymer fibrils around catenulate cells (corresponding to the immature sheath). In time-lapse videos, numerous sheath filaments that extended from the periphery of sheath clumps repeatedly fragmented at the apex of the same fragment, the fragments then aggregated and again elongated, eventually forming a large sheath clump comprising tangled sheaths within two days. In this study, we found that fast microscopic fragmentation, dissociation, re-aggregation and re-elongation events are the basis of the rapid, massive production of Leptothrix sheaths typically observed at macroscopic scales. PMID:27490579

  15. Dissociation and Re-Aggregation of Multicell-Ensheathed Fragments Responsible for Rapid Production of Massive Clumps of Leptothrix Sheaths

    PubMed Central

    Kunoh, Tatsuki; Nagaoka, Noriyuki; McFarlane, Ian R.; Tamura, Katsunori; El-Naggar, Mohamed Y.; Kunoh, Hitoshi; Takada, Jun

    2016-01-01

    Species of the Fe/Mn-oxidizing bacteria Leptothrix produce tremendous amounts of microtubular, Fe/Mn-encrusted sheaths within a few days in outwells of groundwater that can rapidly clog water systems. To understand this mode of rapid sheath production and define the timescales involved, behaviors of sheath-forming Leptothrix sp. strain OUMS1 were examined using time-lapse video at the initial stage of sheath formation. OUMS1 formed clumps of tangled sheaths. Electron microscopy confirmed the presence of a thin layer of bacterial exopolymer fibrils around catenulate cells (corresponding to the immature sheath). In time-lapse videos, numerous sheath filaments that extended from the periphery of sheath clumps repeatedly fragmented at the apex of the same fragment, the fragments then aggregated and again elongated, eventually forming a large sheath clump comprising tangled sheaths within two days. In this study, we found that fast microscopic fragmentation, dissociation, re-aggregation and re-elongation events are the basis of the rapid, massive production of Leptothrix sheaths typically observed at macroscopic scales. PMID:27490579

  16. Microgravity-Driven Optic Nerve/Sheath Biomechanics Simulations

    NASA Technical Reports Server (NTRS)

    Ethier, C. R.; Feola, A.; Myers, J. G.; Nelson, E.; Raykin, J.; Samuels, B.

    2016-01-01

    Visual Impairment and Intracranial Pressure (VIIP) syndrome is a concern for long-duration space flight. Current thinking suggests that the ocular changes observed in VIIP syndrome are related to cephalad fluid shifts resulting in altered fluid pressures [1]. In particular, we hypothesize that increased intracranial pressure (ICP) drives connective tissue remodeling of the posterior eye and optic nerve sheath (ONS). We describe here finite element (FE) modeling designed to understand how altered pressures, particularly altered ICP, affect the tissues of the posterior eye and optic nerve sheath (ONS) in VIIP. METHODS: Additional description of the modeling methodology is provided in the companion IWS abstract by Feola et al. In brief, a geometric model of the posterior eye and optic nerve, including the ONS, was created and the effects of fluid pressures on tissue deformations were simulated. We considered three ICP scenarios: an elevated ICP assumed to occur in chronic microgravity, and ICP in the upright and supine positions on earth. Within each scenario we used Latin hypercube sampling (LHS) to consider a range of ICPs, ONH tissue mechanical properties, intraocular pressures (IOPs) and mean arterial pressures (MAPs). The outcome measures were biomechanical strains in the lamina cribrosa, optic nerve and retina; here we focus on peak values of these strains, since elevated strain alters cell phenotype and induce tissue remodeling. In 3D, the strain field can be decomposed into three orthogonal components, denoted as first, second and third principal strains. RESULTS AND CONCLUSIONS: For baseline material properties, increasing ICP from 0 to 20 mmHg significantly changed strains within the posterior eye and ONS (Fig. 1), indicating that elevated ICP affects ocular tissue biomechanics. Notably, strains in the lamina cribrosa and retina became less extreme as ICP increased; however, within the optic nerve, the occurrence of such extreme strains greatly increased as

  17. 3D Parylene sheath neural probe for chronic recordings

    NASA Astrophysics Data System (ADS)

    Kim, B. J.; Kuo, J. T. W.; Hara, S. A.; Lee, C. D.; Yu, L.; Gutierrez, C. A.; Hoang, T. Q.; Pikov, V.; Meng, E.

    2013-08-01

    Objective. Reliable chronic recordings from implanted neural probes remain a significant challenge; current silicon-based and microwire technologies experience a wide range of biotic and abiotic failure modes contributing to loss of signal quality. Approach. A multi-prong alternative strategy with potential to overcome these hurdles is introduced that combines a novel three dimensional (3D), polymer-based probe structure with coatings. Specifically, the Parylene C sheath-based neural probe is coated with neurotrophic and anti-inflammatory factors loaded onto a Matrigel carrier to encourage the ingrowth of neuronal processes for improved recording quality, reduce the immune response, and promote improved probe integration into brain tissue for reliable, long-term implementation compared to its rigid counterparts. Main results. The 3D sheath structure of the probe was formed by thermal molding of a surface micromachined Parylene C microchannel, with electrode sites lining the interior and exterior regions of the lumen. Electrochemical characterization of the probes via cyclic voltammetry and electrochemical impedance spectroscopy was performed and indicated suitable electrode properties for neural recordings (1 kHz electrical impedance of ∼200 kΩ in vitro). A novel introducer tool for the insertion of the compliant polymer probe into neural tissue was developed and validated both in vitro using agarose gel and in vivo in the rat cerebral cortex. In vivo electrical functionality of the Parylene C-based 3D probes and their suitability for recording the neuronal activity over a 28-day period was demonstrated by maintaining the 1 kHz electrical impedance within a functional range (<400 kΩ) and achieving a reasonably high signal-to-noise ratio for detection of resolvable multi-unit neuronal activity on most recording sites in the probe. Immunohistochemical analysis of the implant site indicated strong correlations between the quality of recorded activity and the

  18. Experimental Studies of Anode Sheath Phenomena in a Hall Thruster Discharge

    SciTech Connect

    L. Dorf; Y. Raitses; N.J. Fisch

    2004-12-17

    Both electron-repelling and electron-attracting anode sheaths in a Hall thruster were characterized by measuring the plasma potential with biased and emissive probes [L. Dorf, Y. Raitses, V. Semenov, and N.J. Fisch, Appl. Phys. Let. 84 (2004) 1070]. In the present work, two-dimensional structures of the plasma potential, electron temperature, and plasma density in the near-anode region of a Hall thruster with clean and dielectrically coated anodes are identified. Possible mechanisms of anode sheath formation in a Hall thruster are analyzed. The path for current closure to the anode appears to be the determining factor in the anode sheath formation process. The main conclusion of this work is that the anode sheath formation in Hall thrusters differs essentially from that in the other gas discharge devices, like a glow discharge or a hollow anode, because the Hall thruster utilizes long electron residence times to ionize rather than high neutral pressures.

  19. The endomembrane sheath: a key structure for understanding the plant cell?

    NASA Technical Reports Server (NTRS)

    Reuzeau, C.; McNally, J. G.; Pickard, B. G.

    1997-01-01

    Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this "streaming", F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations.

  20. A Semianalytical Ion Current Model for Radio Frequency Driven Collisionless Sheaths

    NASA Technical Reports Server (NTRS)

    Bose, Deepak; Govindan, T. R.; Meyyappan, M.; Arnold, Jim (Technical Monitor)

    2001-01-01

    We propose a semianalytical ion dynamics model for a collisionless radio frequency biased sheath. The model uses bulk plasma conditions and electrode boundary condition to predict ion impact energy distribution and electrical properties of the sheath. The proposed model accounts for ion inertia and ion current modulation at bias frequencies that are of the same order of magnitude as the ion plasma frequency. A relaxation equation for ion current oscillations is derived which is coupled with a damped potential equation in order to model ion inertia effects. We find that inclusion of ion current modulation in the sheath model shows marked improvements in the predictions of sheath electrical properties and ion energy distribution function.

  1. Magnetized sheath near positively biased wall between two permanent magnetic plates

    NASA Astrophysics Data System (ADS)

    Sun, Yan; Wei, Zi-an; Ma, J. X.; Jiang, Zheng-qi; Wu, Fei

    2015-06-01

    The characteristics of magnetized electron sheath near a positively biased conducting wall parallel to magnetic field formed between two permanent magnetic plates were experimentally investigated in a double plasma device. The magnetic field strength between the magnetic plates is about 1200 G which is sufficient to magnetize the plasma such that the ion gyroradius is comparable to the electron Debye length. A virtual cathode (or potential dip) structure was found between the electron-rich sheath and bulk plasma. For a given neutral gas pressure, the potential minimum (dip position) remains almost the same for different positive biases on the wall. For a given bias on the wall, however, the electron sheath thickness and the potential drop from the bulk plasma to the dip decrease with the increase of the neutral gas pressure. In addition, the electron sheath and potential dip appear to be wider and deeper in the downstream side of the wall.

  2. The dural sheath of the optic nerve: descriptive anatomy and surgical applications.

    PubMed

    Francois, P; Lescanne, E; Velut, S

    2011-01-01

    The aim of this work was to clarify the descriptive anatomy of the optic dural sheath using microanatomical dissections on cadavers. The orbit is the rostral part of the extradural neural axis compartment; the optic dural sheath forms the central portion of the orbit.In order to describe this specific anatomy, we carefully dissected 5 cadaveric heads (10 orbits) up to the meningeal structure of the orbit and its contents. 1 cadaveric head was reserved for electron microscopy to add to our knowledge of the collagen structure of the optic dural sheath.In this chapter, we describe the anatomy of the interperiostal-dural concept and the anatomy of the orbit. The optic dural sheath contains three portions: the intracranial, the intracanalicular and the intraorbital segment. Each one has specific anatomic relations which result in particular surgical considerations.

  3. 3D Relativistic MHD Simulations of Magnetized Spine-Sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Hardee, Philip E.; Nishikawa, Ken-Ichi

    2007-01-01

    We have performed numerical simulations of weakly and strongly magnetized relativistic jets embedded in a weakly and strongly magnetized stationary or mildly relativistic (0.5c) sheath using the RAISHIN code. In the numerical simulations a jet with Lorentz factor gamma=2.5 is precessed to break the initial equilibrium configuration. Results of the numerical simulations are compared to theoretical predictions from a normal mode-analysis of the linearized RMHD equations describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized moving sheath. The prediction of increased stability of a weakly-magnetized system with mildly relativistic sheath flow to Kelvin-Helmholtz instabilities and the stabilization of a strongly-magnetized system with mildly relativistic sheath flow is confirmed by the numerical simulations.

  4. 3D RMHD Simulations of Magnetized Spine-Sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Hardee, Philip; Nishikawa, Ken-Ichi

    2008-01-01

    We have performed numerical simulations of weakly and strongly magnetized relativistic jets embedded in a weakly and strongly magnetized stationary or mildly relativistic (0.5c) sheath flow using the RAISHIN code. In the numerical simulations a jet with Lorentz factor gamma=2.5 is processed to break the initial equilibrium configuration. Results of the numerical simulations are compared to theoretical predictions from a normal mode analysis of the linearized RMHD equations describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized sheath flow. The prediction of increased stability of a weakly-magnetized system with mildly relativistic sheath flow to Kelvin-Helmholtz instabilities and the stabilization of a strongly magnetized system with mildly relativistic sheath flow is confirmed by the numerical simulations.

  5. 3D RMHD Simulations of Magnetized Spine-sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Hardee, Phillip; Ken-Ichi, Nishikawa

    2008-01-01

    We have performed numerical simulations of weakly and strongly magnetized relativistic jets embedded in a weakly and strongly magnetized stationary or mildly relativistic'(0.5c) sheath flow using the RAISHIN code. In the numerical simulations a jet with Lorentz factor gamma=2.5 is processed to break the initial equilibrium configuration. Results of the numerical simulations are compared to theoretical predictions from a normal mode analysis of the linearized RMHD equations describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized sheath flow. The prediction of increased stability of a weakly-magnetized system with mildly relativistic sheath flow to Kelvin-Helmholtz instabilities and the stabilization of a strongly-magnetized system with mildly relativistic sheath flow is confirmed by the numerical simulations.

  6. Sheath-limited unipolar induction in the solar wind. [plasma interactions with solar system bodies

    NASA Technical Reports Server (NTRS)

    Srnka, L. J.

    1975-01-01

    A model of the steady-state interaction between the solar wind and an electrically conducting body having neither an atmosphere nor an intrinsic magnetic field sufficient enough to deflect the plasma flow is presented which considers some effects of a plasma surface sheath on unipolar induction. The Sonett-Colburn (1967, 1968) unipolar dynamo model is reviewed, and it is noted that the unipolar dynamo response of an electrically conducting body in the solar wind's motional field can be controlled by sheath effects in certain cases where the body radius is less than a certain critical value. It is shown that sheath effects do not limit the unipolar response of the moon or Mercury since their body radii are much larger than their critical radii. Sheath effects are also considered for asteroids, the Martian satellites, the irregular Jovian satellites, the outer satellites of Saturn, and meteorite parent bodies in a primordial enhanced solar wind.

  7. Polyacrylonitrile nanofibers prepared using coaxial electrospinning with LiCl solution as sheath fluid

    NASA Astrophysics Data System (ADS)

    Yu, Deng-Guang; Lu, Ping; Branford-White, Christopher; Yang, Jun-He; Wang, Xia

    2011-10-01

    A modified coaxial electrospinning process including an electrolyte solution as sheath fluid was used for preparing high quality polymer nanofibers. A series of polyacrylonitrile (PAN) nanofibers were fabricated utilizing a coaxial electrospinning containing LiCl in N, N-dimethylacetamide (DMAc) as the sheath fluid. FESEM results demonstrated that the sheath LiCl solutions have a significant influence on the quality of PAN nanofibers. Nanofibers with smaller diameters, smoother surfaces and uniform structures were successfully prepared. The diameters of nanofibers were controlled by adjusting the conductivity of the sheath fluid over a suitable range and this was determined by varying LiCl concentrations. The influence of the effect of LiCl on the formation of PAN fibers is discussed and it is concluded that coaxial electrospinning with electrolyte solutions is a convenient and facile process for achieving high quality polymer nanofibers.

  8. Three dimensional space charge model for large high voltage satellites. [plasma sheath

    NASA Technical Reports Server (NTRS)

    Cooks, D.; Parker, L. W.; Mccoy, J. E.

    1980-01-01

    High power solar arrays for satellite power systems with dimensions of kilometers, and with tens of kilovolts distributed over their surface face many plasma interaction problems that must be properly anticipated. In most cases, the effects cannot be adequately modeled without detailed knowledge of the plasma sheath structure and space charge effects. Two computer programs were developed to provide fully self consistent plasma sheath models in three dimensions as a result of efforts to model the experimental plasma sheath studies at NASA/JSC. Preliminary results indicate that for the conditions considered, the Child-Langmuir diode theory can provide a useful estimate of the plasma sheath thickness. The limitations of this conclusion are discussed. Some of the models presented exhibit the strong ion focusing observed in the JSC experiments.

  9. Effect of flexor sheath integrity on nutrient uptake by chicken flexor tendons

    SciTech Connect

    Peterson, W.W.; Manske, P.R.; Lesker, P.A.

    1985-12-01

    The effect of varying degrees of flexor sheath integrity (sheath excised, incised, or incised and repaired) on the uptake of /sub 2/H-proline by chicken flexor tendons in Zone II was studied. The tendons were either: normal and uninjured, lacerated and repaired, or uninjured except for vinculum longum ligation. Different degrees of sheath integrity did not influence the uptake of /sub 2/H-proline by the tendons. The tendon does not appear to be dependent on a synovial environment for nutrients and is capable of obtaining these nutrients by diffusion from the surrounding extracellular tissue fluid. Diffusion is the primary nutrient pathway to the flexor tendon in this area, because removing its major vascular attachment (i.e., the vinculum longum) did not effect proline uptake. Careful closure of the sheath with restoration of a synovial environment does not appear to be necessary for tendon nutrition.

  10. A Simplified Model Joining the Sheath and the Plasma in Electronegative Plasmas

    NASA Astrophysics Data System (ADS)

    Fernández Palop, J. I.; Ballesteros, J.; Hernández, M. A.; Crespo, R. Morales; Del Pino, S. Borrego

    2004-02-01

    An extension of the previous work which only dealt with the sheath zone is used to analyze the wall-plasma interaction in electronegative plasmas. Ionization is introduced as the presheath mechanism. This extension includes the joining of the sheath and the plasma solutions. For certain plasma parameters a stratified presheath is obtained. In this case, the plasma and the sheath solutions are matched in a very simplified way, by introducing a discontinuity in the electric field. This discontinuity is equivalent to consideration of a negatively charged layer between the presheath and the sheath. The parameter space region in which this matching should be made has been delimited. The model includes the previous one in the limiting case of no ionization.

  11. The structure and development of the starch sheath in pea epicotyls

    NASA Technical Reports Server (NTRS)

    Sack, D. F.

    1985-01-01

    Graviperception in plant stems is thought to occur in endodermal cells differentiated as a starch sheath, but little is known about the ultrastructure of these cells in dicots. The structure of the pea starch sheath was studied with respect to gravity and to development in order to determine whether symplastic or apoplastic blockages exist and to describe any intracellular polarity. Amyloplasts increase in size towards the base of the epicotyl hook but are not consistently sedimented until the cells enter the zone exhibiting gravicurvature below the hook. The starch sheath cells are connected to each other and to cells of the cortex and the stele by plasmodesmata. A casparian strip exists in older endodermal cells but not at the stage that the endodermis is differentiated as a starch sheath. Amyloplasts were frequently observed in apparent contact with endoplasmic reticulum.

  12. Enhancing resolution of free-flow zone electrophoresis via a simple sheath-flow sample injection.

    PubMed

    Yang, Ying; Kong, Fan-Zhi; Liu, Ji; Li, Jun-Min; Liu, Xiao-Ping; Li, Guo-Qing; Wang, Ju-Fang; Xiao, Hua; Fan, Liu-Yin; Cao, Cheng-Xi; Li, Shan

    2016-07-01

    In this work, a simple and novel sheath-flow sample injection method (SFSIM) is introduced to reduce the band broadening of free-flow zone electrophoresis separation in newly developed self-balance free-flow electrophoresis instrument. A needle injector was placed in the center of the separation inlet, into which the BGE and sample solution were pumped simultaneously. BGE formed sheath flow outside the sample stream, resulting in less band broadening related to hydrodynamics and electrodynamics. Hemoglobin and C-phycocyanin were successfully separated by the proposed method in contrast to the poor separation of free-flow electrophoresis with the traditional injection method without sheath flow. About 3.75 times resolution enhancement could be achieved by sheath-flow sample injection method. PMID:27121853

  13. The endomembrane sheath: a key structure for understanding the plant cell?

    PubMed

    Reuzeau, C; McNally, J G; Pickard, B G

    1997-01-01

    Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this "streaming", F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations. PMID:11542471

  14. ICME-driven sheath regions deplete the outer radiation belt electrons

    NASA Astrophysics Data System (ADS)

    Hietala, H.; Kilpua, E. K.; Turner, D. L.

    2013-12-01

    It is an outstanding question in space weather and solar wind-magnetosphere interaction studies, why some storms result in an increase of the outer radiation belt electron fluxes, while others deplete them or produce no change. One approach to this problem is to look at differences in the storm drivers. Traditionally drivers have been classified to Stream Interaction Regions (SIRs) and Interplanetary Coronal Mass Ejections (ICMEs). However, an 'ICME event' is a complex structure: The core is a magnetic cloud (MC; a clear flux rope structure). If the mass ejection is fast enough, it can drive a shock in front of it. This leads to the formation of a sheath region between the interplanetary shock and the leading edge of the MC. While both the sheath and the MC feature elevated solar wind speed, their other properties are very different. For instance, the sheath region has typically a much higher dynamic pressure than the magnetic cloud. Moreover, the sheath region has a high power in magnetic field and dynamic pressure Ultra Low Frequency (ULF) range fluctuations, while the MC is characterised by an extremely smooth magnetic field. Magnetic clouds have been recognised as important drivers magnetospheric activity since they can comprise long periods of very large southward Interplanetary Magnetic Field (IMF). Nevertheless, previous studies have shown that sheath regions can also act as storm drivers. In this study, we analyse the effects of ICME-driven sheath regions on the relativistic electron fluxes observed by GOES satellites on the geostationary orbit. We perform a superposed epoch analysis of 31 sheath regions from solar cycle 23. Our results show that the sheaths cause an approximately one order of magnitude decrease in the 24h-averaged electron fluxes. Typically the fluxes also stay below the pre-event level for more than two days. Further analysis reveals that the decrease does not depend on, e.g., whether the sheath interval contains predominantly northward

  15. Temperature response of bundle-sheath conductance in maize leaves.

    PubMed

    Yin, Xinyou; van der Putten, Peter E L; Driever, Steven M; Struik, Paul C

    2016-04-01

    A small bundle-sheath conductance (g bs) is essential for the C4 CO2-concentrating mechanism to suppress photorespiration effectively. To predict the productivity of C4 crops accurately under global warming, it is necessary to examine whether and how g bs responds to temperature. We investigated the temperature response of g bs in maize by fitting a C4 photosynthesis model to combined gas exchange and chlorophyll fluorescence measurements of irradiance and CO2 response curves at 21% and 2% O2 within the range of 13.5-39 °C. The analysis was based on reported kinetic constants of C4 Rubisco and phosphoenolpyruvate carboxylase and temperature responses of C3 mesophyll conductance (g m). The estimates of g bs varied greatly with leaf temperature. The temperature response of g bs was well described by the peaked Arrhenius equation, with the optimum temperature being ~34 °C. The assumed temperature responses of g m had only a slight impact on the temperature response of g bs In contrast, using extreme values of some enzyme kinetic constants changed the shape of the response, from the peaked optimum response to the non-peaked Arrhenius pattern. Further studies are needed to confirm such an Arrhenius response pattern from independent measurement techniques and to assess whether it is common across C4 species. PMID:26969744

  16. Evolution and Development of Hertwig’s Epithelial Root Sheath

    PubMed Central

    Luan, Xianghong; Ito, Yoshihiro; Diekwisch, Thomas G.H.

    2009-01-01

    Periodontal regeneration and tissue engineering has re-awakened interest in the role of Hertwig’s Epithelial Root Sheath (HERS), an epithelial tissue layer first discovered in amphibians more than a century ago. Using developmental, evolutionary, and cell biological approaches we have therefore performed a careful analysis of the role of HERS in root formation and compared our data with clinical findings. Our developmental studies revealed HERS as a transient structure assembled in the early period of root formation and elongation and subsequently fenestrated and reduced to epithelial rests of Malassez (ERM). Our comparative evolutionary studies indicated that HERS fenestration was closely associated with the presence of a periodontal ligament and a gomphosis-type attachment apparatus in crocodilians and mammals. Based on these studies, we are proposing that HERS plays an important role in the regulation and maintenance of periodontal ligament space and function. Additional support for this hypothesis was rendered by our meta-analysis of recent clinical reports related to HERS function. PMID:16450392

  17. Temperature response of bundle-sheath conductance in maize leaves

    PubMed Central

    Yin, Xinyou; van der Putten, Peter E.L.; Driever, Steven M.; Struik, Paul C.

    2016-01-01

    A small bundle-sheath conductance (g bs) is essential for the C4 CO2-concentrating mechanism to suppress photorespiration effectively. To predict the productivity of C4 crops accurately under global warming, it is necessary to examine whether and how g bs responds to temperature. We investigated the temperature response of g bs in maize by fitting a C4 photosynthesis model to combined gas exchange and chlorophyll fluorescence measurements of irradiance and CO2 response curves at 21% and 2% O2 within the range of 13.5–39 °C. The analysis was based on reported kinetic constants of C4 Rubisco and phosphoenolpyruvate carboxylase and temperature responses of C3 mesophyll conductance (g m). The estimates of g bs varied greatly with leaf temperature. The temperature response of g bs was well described by the peaked Arrhenius equation, with the optimum temperature being ~34 °C. The assumed temperature responses of g m had only a slight impact on the temperature response of g bs. In contrast, using extreme values of some enzyme kinetic constants changed the shape of the response, from the peaked optimum response to the non-peaked Arrhenius pattern. Further studies are needed to confirm such an Arrhenius response pattern from independent measurement techniques and to assess whether it is common across C4 species. PMID:26969744

  18. Ultrasonographic measurement of optic nerve sheath diameter in normal dogs.

    PubMed

    Lee, Hee-Chun; Choi, Ho-Jung; Choi, Min-Cheol; Yoon, Jung-Hee

    2003-12-01

    This study was carried out to assess the feasibility of ultrasonographic measurements of the optic nerve sheath diameter (ONSD) in normal dogs and evaluate the effect of breed, sex, body weight and age on biometry of ONSD. The ONSDs were evaluated in 15 dogs (10-50 months old) with normal eye (7 Yorkshire terrier and 8 Maltese). Ultrasonographic measurements of the ONSD were carried out at a constant position located 5 mm behind the optic disc. Eyes were collected immediately after euthanasia, and were used for saline immersion technique and direct measurement by calipers for biometry of ONSD. In this study, there was no significant difference of ONSD between the left and the right eyes, and was no significant difference among ONSD values obtained from ultrasonographical method, saline immersion technique and direct measurement (k=0.95). Also, there was no correlations between ONSD and sex, body weight and age, but was significant between the mean ONSD of Yorkshire terrier and Maltese (p<0.01). The mean ONSD of Yorkshire terrier was 2.10 +/- 0.22 mm and Maltese was 1.63 +/- 0.23 mm. This study suggests that ultrasonographic measurements is useful method for biometry of the ONSD in normal dogs and provides baseline information for the study of evaluating ONSD in various breeds and diagnosing several diseases with the change of the ONSD.

  19. Chitosan-sheath and chitin-core nanowhiskers.

    PubMed

    Pereira, Antonio G B; Muniz, Edvani C; Hsieh, You-Lo

    2014-07-17

    Chitosan-sheath and α-chitin-core nanowhiskers (CsNWs) have been successfully generated by surface deacetylation of chitin nanowhiskers (CtNWs) in the never-dried state. Acid hydrolysis (3N HCl, 30 mL/g, 104°C) of pure chitin derived from crab shell yielded 65% 4-10nm thick, 16 nm wide and 214 nm long chitin whiskers (CtNWs) that were 86% crystalline and 81% acetylated. Surface deacetylation of CtNWs was robust in their never-dried state in 50% NaOH at a moderate 50°C for 6h, yielding 92% CsNWs. All deacetylated CsNWs retain the same α-chitin crystalline core at reduced 50% crystallinity and similar dimensions (4-12 nm thick, 15 nm wide, 247 long) as CtNWs, but reduced 60% acetylation reflecting the deacetylated surface layers. Progressive surface deacetylation was evident by the increased IP as well as increased positive charges under acidic pH and reduced negative charges at alkaline pH with increasing reaction time.

  20. Downsized Sheath-Core Conducting Fibers for Weavable Superelastic Wires, Biosensors, Supercapacitors, and Strain Sensors.

    PubMed

    Wang, Hongyan; Liu, Zunfeng; Ding, Jianning; Lepró, Xavier; Fang, Shaoli; Jiang, Nan; Yuan, Ninyi; Wang, Run; Yin, Qu; Lv, Wei; Liu, Zhongsheng; Zhang, Mei; Ovalle-Robles, Raquel; Inoue, Kanzan; Yin, Shougen; Baughman, Ray H

    2016-07-01

    Hair-like-diameter superelastic conducting fibers, comprising a buckled carbon nanotube sheath on a rubber core, are fabricated, characterized, and deployed as weavable wires, biosensors, supercapacitors, and strain sensors. These downsized sheath-core fibers provide the demonstrated basis for glucose sensors, supercapacitors, and electrical interconnects whose performance is undegraded by giant strain, as well as ultrafast strain sensors that exploit strain-dependent capacitance changes.

  1. Highly Compliant Vascular Grafts with Gelatin-Sheathed Coaxially Structured Nanofibers.

    PubMed

    Nagiah, Naveen; Johnson, Richard; Anderson, Roy; Elliott, Winston; Tan, Wei

    2015-12-01

    We have developed three types of materials composed of polyurethane-gelatin, polycaprolactone-gelatin, or polylactic acid-gelatin nanofibers by coaxially electrospinning the hydrophobic core and gelatin sheath with a ratio of 1:5 at fixed concentrations. Results from attenuated total reflection-Fourier transformed infrared spectroscopy demonstrated the gelatin coating around nanofibers in all of the materials. Transmission electron microscopy images further displayed the core-sheath structures showing the core-to-sheath thickness ratio varied greatly with the highest ratio found in polyurethane-gelatin nanofibers. Scanning electron microscopy images revealed similar, uniform fibrous structures in all of the materials, which changed with genipin cross-linking due to interfiber interactions. Thermal analyses revealed varied interactions between the hydrophilic sheath and hydrophobic core among the three materials, which likely caused different core-sheath structures, and thus physicomechanical properties. The addition of gelatin around the hydrophobic polymer and their interactions led to the formation of graft scaffolds with tissue-like viscoelasticity, high compliance, excellent swelling capability, and absence of water permeability while maintaining competent tensile modulus, burst pressure, and suture retention. The hydrogel-like characteristics are advantageous for vascular grafting use, because of the capability of bypassing preclotting prior to implantation, retaining vascular fluid volume, and facilitating molecular transport across the graft wall, as shown by coculturing vascular cells sandwiched over a thick-wall scaffold. Varied core-sheath interactions within scaffolding nanofibers led to differences in graft functional properties such as water swelling ratio, compliance, and supporting growth of cocultured vascular cells. The PCL-gelatin scaffold with thick gelatin-sheathed nanofibers demonstrated a more compliant structure, elastic mechanics, and high

  2. Downsized Sheath-Core Conducting Fibers for Weavable Superelastic Wires, Biosensors, Supercapacitors, and Strain Sensors.

    PubMed

    Wang, Hongyan; Liu, Zunfeng; Ding, Jianning; Lepró, Xavier; Fang, Shaoli; Jiang, Nan; Yuan, Ninyi; Wang, Run; Yin, Qu; Lv, Wei; Liu, Zhongsheng; Zhang, Mei; Ovalle-Robles, Raquel; Inoue, Kanzan; Yin, Shougen; Baughman, Ray H

    2016-07-01

    Hair-like-diameter superelastic conducting fibers, comprising a buckled carbon nanotube sheath on a rubber core, are fabricated, characterized, and deployed as weavable wires, biosensors, supercapacitors, and strain sensors. These downsized sheath-core fibers provide the demonstrated basis for glucose sensors, supercapacitors, and electrical interconnects whose performance is undegraded by giant strain, as well as ultrafast strain sensors that exploit strain-dependent capacitance changes. PMID:27135200

  3. Self-consistent simulation of high-frequency driven plasma sheaths

    NASA Astrophysics Data System (ADS)

    Shihab, Mohammed; Eremin, Denis; Mussenbrock, Thomas; Brinkmann, Ralf

    2011-10-01

    Low pressure capacitively coupled plasmas are widely used in plasma processing and microelectronics industry. Understanding the dynamics of the boundary sheath is a fundamental problem. It controls the energy and angular distribution of ions bombarding the electrode, which in turn affects the surface reaction rate and the profile of microscopic features. In this contribution, we investigate the dynamics of plasma boundary sheaths by means of a kinetic self-consistent model, which is able to resolve the ion dynamics. Asymmetric sheath dynamics is observed for the intermediate RF regime, i.e., in the regime where the ion plasma frequency is equal to the driving frequency. The ion inertia causes an additional phase difference between the expansion and the contraction phase of the plasma sheath and an asymmetry for the ion energy distribution bimodal shape. A comparison with experimental results and particle in cell simulations is performed. Low pressure capacitively coupled plasmas are widely used in plasma processing and microelectronics industry. Understanding the dynamics of the boundary sheath is a fundamental problem. It controls the energy and angular distribution of ions bombarding the electrode, which in turn affects the surface reaction rate and the profile of microscopic features. In this contribution, we investigate the dynamics of plasma boundary sheaths by means of a kinetic self-consistent model, which is able to resolve the ion dynamics. Asymmetric sheath dynamics is observed for the intermediate RF regime, i.e., in the regime where the ion plasma frequency is equal to the driving frequency. The ion inertia causes an additional phase difference between the expansion and the contraction phase of the plasma sheath and an asymmetry for the ion energy distribution bimodal shape. A comparison with experimental results and particle in cell simulations is performed. The financial support from the Federal Ministry of Education and Research within the frame of

  4. A Rapamycin-Releasing Perivascular Polymeric Sheath Produces Highly Effective Inhibition of Intimal Hyperplasia

    PubMed Central

    Yu, Xaohua; Takayama, Toshio; Goel, Shakti A.; Shi, Xudong; Zhou, Yifan; Kent, K. Craig; Murphy, William L.; Guo, Lian-Wang

    2014-01-01

    Intimal hyperplasia produces restenosis (re-narrowing) of the vessel lumen following vascular intervention. Drugs that inhibit intimal hyperplasia have been developed, however there is currently no clinical method of perivascular drug-delivery to prevent restenosis following open surgical procedures. Here we report a poly(ε-caprolactone) (PCL) sheath that is highly effective in preventing intimal hyperplasia through perivascular delivery of rapamycin. We first screened a series of bioresorbable polymers, i.e., poly(lactide-co-glycolide) (PLGA), poly(lactic acid) (PLLA), PCL, and their blends, to identify desired release kinetics and sheath physical properties. Both PLGA and PLLA sheaths produced minimal (<30%) rapamycin release within 50 days in PBS buffer. In contrast, PCL sheaths exhibited more rapid and near-linear release kinetics, as well as durable integrity (>90 days) as evidenced in both scanning electron microscopy and subcutaneous embedding experiments. Moreover, a PCL sheath deployed around balloon-injured rat carotid arteries was associated with a minimum rate of thrombosis compared to PLGA and PLLA. Morphometric analysis and immunohistochemistry revealed that rapamycin-loaded perivascular PCL sheaths produced pronounced (85%) inhibition of intimal hyperplasia (0.15±0.05 vs 1.01±0.16), without impairment of the luminal endothelium, the vessel’s anti-thrombotic layer. Our data collectively show that a rapamycin-loaded PCL delivery system produces substantial mitigation of neointima, likely due to its favorable physical properties leading to a stable yet flexible perivascular sheath and steady and prolonged release kinetics. Thus, a PCL sheath may provide useful scaffolding for devising effective perivascular drug delivery particularly suited for preventing restenosis following open vascular surgery. PMID:24852098

  5. Benign Nerve Sheath Myxoma in an Infant Misdiagnosed as Infantile Digital Fibromatosis.

    PubMed

    Güngör, Şule; Şişman, Servet; Kocaturk, Emek; Oguz Topal, Ilteris; Yıldırım, Selda

    2016-07-01

    Herein we present the case of a 16-month boy, clinically diagnosed with infantile digital fibromatosis, but 9 months after continued growth, the mass was excised and the histopathologic diagnosis was that of a benign nerve sheath myxoma. We present this case to emphasize that nerve sheath myxomas (also known as myxoid neurothekeoma) should be included in the differential diagnosis of dermal nodules in infants. PMID:27196676

  6. Highly Compliant Vascular Grafts with Gelatin-Sheathed Coaxially Structured Nanofibers.

    PubMed

    Nagiah, Naveen; Johnson, Richard; Anderson, Roy; Elliott, Winston; Tan, Wei

    2015-12-01

    We have developed three types of materials composed of polyurethane-gelatin, polycaprolactone-gelatin, or polylactic acid-gelatin nanofibers by coaxially electrospinning the hydrophobic core and gelatin sheath with a ratio of 1:5 at fixed concentrations. Results from attenuated total reflection-Fourier transformed infrared spectroscopy demonstrated the gelatin coating around nanofibers in all of the materials. Transmission electron microscopy images further displayed the core-sheath structures showing the core-to-sheath thickness ratio varied greatly with the highest ratio found in polyurethane-gelatin nanofibers. Scanning electron microscopy images revealed similar, uniform fibrous structures in all of the materials, which changed with genipin cross-linking due to interfiber interactions. Thermal analyses revealed varied interactions between the hydrophilic sheath and hydrophobic core among the three materials, which likely caused different core-sheath structures, and thus physicomechanical properties. The addition of gelatin around the hydrophobic polymer and their interactions led to the formation of graft scaffolds with tissue-like viscoelasticity, high compliance, excellent swelling capability, and absence of water permeability while maintaining competent tensile modulus, burst pressure, and suture retention. The hydrogel-like characteristics are advantageous for vascular grafting use, because of the capability of bypassing preclotting prior to implantation, retaining vascular fluid volume, and facilitating molecular transport across the graft wall, as shown by coculturing vascular cells sandwiched over a thick-wall scaffold. Varied core-sheath interactions within scaffolding nanofibers led to differences in graft functional properties such as water swelling ratio, compliance, and supporting growth of cocultured vascular cells. The PCL-gelatin scaffold with thick gelatin-sheathed nanofibers demonstrated a more compliant structure, elastic mechanics, and high

  7. Synaptic vesicle release regulates myelin sheath number of individual oligodendrocytes in vivo.

    PubMed

    Mensch, Sigrid; Baraban, Marion; Almeida, Rafael; Czopka, Tim; Ausborn, Jessica; El Manira, Abdeljabbar; Lyons, David A

    2015-05-01

    The myelination of axons by oligodendrocytes markedly affects CNS function, but how this is regulated by neuronal activity in vivo is not known. We found that blocking synaptic vesicle release impaired CNS myelination by reducing the number of myelin sheaths made by individual oligodendrocytes during their short period of formation. We also found that stimulating neuronal activity increased myelin sheath formation by individual oligodendrocytes. These data indicate that neuronal activity regulates the myelinating capacity of single oligodendrocytes.

  8. Instability, Collapse and Oscillation of Sheaths Caused by Secondary Electron Emission

    SciTech Connect

    M.D. Campanell, A.V. Khrabrov and I.D. Kaganovich

    2013-01-03

    The Debye sheath is shown to be unstable under general conditions. For surface materials with sufficient secondary electron emission (SEE) yields, the surface's current-voltage characteristic has an unstable branch when the bulk plasma temperature (Te ) exceeds a critical value, or when there are fast electron populations present. The plasma-surface interaction becomes dynamic where the sheath may undergo spontaneous transitions or oscillations. Using particle-in-cell simulations, we analyze sheath instabilities occurring in a high Te plasma slab bounded by walls with SEE. As the plasma evolves, whenever the sheath enters an unstable state, its amplitude rapidly collapses, allowing a large flux of previously trapped electrons to hit the wall. These hot electrons induce more than one secondary on average, causing a net loss of electrons from the wall. The sheath collapse quenches when the surface charge becomes positive because the attractive field inhibits further electrons from escaping. Sheath instabilities influence the current balance, energy loss, cross-B-field transport and even the bulk plasma properties. Implications for discharges including Hall thrusters are discussed. More generally, the results show that common theories that treat emission as a fixed (time-independent) "coefficient" do not capture the full extent of SEE effects.

  9. Functional analysis of OsPGIP1 in rice sheath blight resistance.

    PubMed

    Wang, Rui; Lu, Liaoxun; Pan, Xuebiao; Hu, Zongliang; Ling, Fei; Yan, Yan; Liu, Yemao; Lin, Yongjun

    2015-01-01

    As one of the most devastating diseases of rice, sheath blight causes severe rice yield loss. However, little progress has been made in rice breeding for sheath blight resistance. It has been reported that polygalacturonase inhibiting proteins can inhibit the degradation of the plant cell wall by polygalacturonases from pathogens. Here, we prokaryotically expressed and purified OsPGIP1 protein, which was verified by Western blot analysis. Activity assay confirmed the inhibitory activity of OsPGIP1 against the PGase from Rhizoctonia solani. In addition, the location of OsPGIP1 was determined by subcellular localization. Subsequently, we overexpressed OsPGIP1 in Zhonghua 11 (Oryza sativa L. ssp. japonica), and applied PCR and Southern blot analysis to identify the positive T0 transgenic plants with single-copy insertions. Germination assay of the seeds from T1 transgenic plants was carried out to select homozygous OsPGIP1 transgenic lines, and the expression levels of OsPGIP1 in these lines were analyzed by quantitative real-time PCR. Field testing of R. solani inoculation showed that the sheath blight resistance of the transgenic rice was significantly improved. Furthermore, the levels of sheath blight resistance were in accordance with the expression levels of OsPGIP1 in the transgenic lines. Our results reveal the functions of OsPGIP1 and its resistance mechanism to rice sheath blight, which will facilitate rice breeding for sheath blight resistance.

  10. The magnetized sheath of a dusty plasma with nanosize dust grains

    SciTech Connect

    Mehdipour, H.; Foroutan, G.

    2010-08-15

    The magnetized sheath of a dusty plasma is investigated via numerical simulations of stationary multifluid equations by taking into account the electric, magnetic, gravitational, ion drag, neutral drag, and thermophoretic forces. Dependence of the sheath properties on the characteristics of the magnetic field and plasma parameters is explored. The sheath dynamics is mainly governed by the electric and ion drag forces and the effect of gravitation is negligible. The sheath demonstrates a nonmonotonic behavior against variations of the magnetic intensity and its angle of incidence. The sheath thickness and the maximum of dust density distribution decrease with increasing the ion to electron density ratio at the sheath edge, but increase with growing electron temperature and the positive temperature gradient of the neutrals. The effects of ion drag are similar to those of the gravitational force as both of them accelerate the dust to the wall. By a suitable configuration of the temperature gradient in the neutral gas, thermophoretic force can be utilized to deposit the building units of nanostructures on a substrate or remove any unwanted contaminant from its neighborhood.

  11. Hertwig's epithelial root sheath cells do not transform into cementoblasts in rat molar cementogenesis.

    PubMed

    Yamamoto, Tsuneyuki; Takahashi, Shigeru

    2009-12-01

    It is generally accepted that cementoblasts originate in the process of differentiation of the mesenchymal cells of the dental follicle. Recently, a different hypothesis for the origin of cementoblasts has been proposed. Hertwig's epithelial root sheath cells undergo the epithelial-mesenchymal transformation to differentiate into cementoblasts. To elucidate whether the epithelial-mesenchymal transformation occurs in the epithelial sheath, developing rat molars were examined by keratin-vimentin and Runx2 (runt-related transcription factor 2)-keratin double immunostaining. In both acellular and cellular cementogenesis, epithelial sheath and epithelial cells derived from the epithelial sheath expressed keratin, but did not express vimentin or Runx2. Dental follicle cells and cementoblasts, however, expressed vimentin and Runx2, but did not express keratin. No cells showed coexisting keratin-vimentin or Runx2-keratin staining. These findings suggest that there is no intermediate phenotype transforming epithelial to mesenchymal cells, and that epithelial sheath cells do not generate mineralized tissue. This study concludes that the epithelial-mesenchymal transformation does not occur in Hertwig's epithelial root sheath in rat acellular or cellular cementogenesis and that the dental follicle is the origin of cementoblasts, as has been proposed in the original hypothesis. PMID:19716687

  12. GRMHD/RMHD Simulations and Stability of Magnetized Spine-Sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Hardee, Philip; Mizuno, Yosuke; Nishikawa, Ken-Ichi

    2007-01-01

    A new general relativistic magnetohydrodynamics (GRMHD ) code "RAISHIN" used to simulate jet generation by rotating and non-rotating black holes with a geometrically thin Keplarian accretion disk finds that the jet develops a spine-sheath structure in the rotating black hole case. Spine-sheath structure and strong magnetic fields significantly modify the Kelvin-Helmholtz (KH) velocity shear driven instability. The RAISHIN code has been used in its relativistic magnetohydrodynamic (RMHD) configuration to study the effects of strong magnetic fields and weakly relativistic sheath motion, cl2, on the KH instability associated with a relativistic, Y = 2.5, jet spine-sheath interaction. In the simulations sound speeds up to ? c/3 and Alfven wave speeds up to ? 0.56 c are considered. Numerical simulation results are compared to theoretical predictions from a new normal mode analysis of the RMHD equations. Increased stability of a weakly magnetized system resulting from c/2 sheath speeds and stabilization of a strongly magnetized system resulting from d 2 sheath speeds is found.

  13. Hydrophobicity-induced selective covering of carbon nanotubes with sol gel sheaths achieved by ultrasound assistance

    NASA Astrophysics Data System (ADS)

    Park, Ki Chul; Mahiko, Tomoaki; Morimoto, Shingo; Takeuchi, Kenji; Endo, Morinobu

    2008-09-01

    A simple construction of sol-gel sheaths onto the surface of multi-walled carbon nanotubes (MWCNTs) has been carried out in water by a hydrophobicity-induced covering with the assistance of ultrasound. The ultrasound assistance prevents in water an unregulated agglomeration induced by the hydrophobicity of MWCNTs and phenyl-containing sols, leading to a selective construction of sol-gel sheaths on the nanotube surface. The phenyl groups of the resulting sol-gel sheaths were successfully removed by air-oxidation to provide the MWCNTs covered with amorphous SiO 2 sheaths. The effect of the SiO 2 sheaths on the electrical and thermal properties of the SiO 2-MWCNT nanocomposites was evaluated from the electrical resistivities of the nanocomposites with two different SiO 2 concentrations and the thermal conductivities of their phenol-resin composites. The results indicate that the small increase of the SiO 2 concentration remarkably increases the electrical resistivity of the SiO 2-MWCNT nanocomposites. Furthermore, the SiO 2 sheaths have more directly influenced the thermal property of the polymer composites than the inside nanotubes.

  14. Movement and structure of mitochondria in oligodendrocytes and their myelin sheaths.

    PubMed

    Rinholm, Johanne E; Vervaeke, Koen; Tadross, Michael R; Tkachuk, Ariana N; Kopek, Benjamin G; Brown, Timothy A; Bergersen, Linda H; Clayton, David A

    2016-05-01

    Mitochondria play several crucial roles in the life of oligodendrocytes. During development of the myelin sheath they are essential providers of carbon skeletons and energy for lipid synthesis. During normal brain function their consumption of pyruvate will be a key determinant of how much lactate is available for oligodendrocytes to export to power axonal function. Finally, during calcium-overload induced pathology, as occurs in ischemia, mitochondria may buffer calcium or induce apoptosis. Despite their important functions, very little is known of the properties of oligodendrocyte mitochondria, and mitochondria have never been observed in the myelin sheaths. We have now used targeted expression of fluorescent mitochondrial markers to characterize the location and movement of mitochondria within oligodendrocytes. We show for the first time that mitochondria are able to enter and move within the myelin sheath. Within the myelin sheath the highest number of mitochondria was in the cytoplasmic ridges along the sheath. Mitochondria moved more slowly than in neurons and, in contrast to their behavior in neurons and astrocytes, their movement was increased rather than inhibited by glutamate activating NMDA receptors. By electron microscopy we show that myelin sheath mitochondria have a low surface area of cristae, which suggests a low ATP production. These data specify fundamental properties of the oxidative phosphorylation system in oligodendrocytes, the glial cells that enhance cognition by speeding action potential propagation and provide metabolic support to axons.

  15. Solid dispersions in the form of electrospun core-sheath nanofibers

    PubMed Central

    Yu, Deng-Guang; Zhu, Li-Min; Branford-White, Christopher J; Yang, Jun-He; Wang, Xia; Li, Ying; Qian, Wei

    2011-01-01

    Background The objective of this investigation was to develop a new type of solid dispersion in the form of core-sheath nanofibers using coaxial electrospinning for poorly water-soluble drugs. Different functional ingredients can be placed in various parts of core-sheath nanofibers to improve synergistically the dissolution and permeation properties of encapsulated drugs and to enable drugs to exert their actions. Methods Using acyclovir as a model drug, polyvinylpyrrolidone as the hydrophilic filament-forming polymer matrix, sodium dodecyl sulfate as a transmembrane enhancer, and sucralose as a sweetener, core-sheath nanofibers were successfully prepared, with the sheath part consisting of polyvinylpyrrolidone, sodium dodecyl sulfate, and sucralose, and the core part composed of polyvinylpyrrolidone and acyclovir. Results The core-sheath nanofibers had an average diameter of 410 ± 94 nm with a uniform structure and smooth surface. Differential scanning calorimetry and x-ray diffraction results demonstrated that acyclovir, sodium dodecyl sulfate, and sucralose were well distributed in the polyvinylpyrrolidone matrix in an amorphous state due to favoring of second-order interactions. In vitro dissolution and permeation studies showed that the core-sheath nanofiber solid dispersions could rapidly release acyclovir within one minute, with an over six-fold increased permeation rate across the sublingual mucosa compared with that of crude acyclovir particles. Conclusion The study reported here provides an example of the systematic design, preparation, characterization, and application of a novel type of solid dispersion consisting of multiple components and structural characteristics. PMID:22228995

  16. Application of Spray Foam Insulation Under Plywood and Oriented Strand Board Roof Sheathing

    SciTech Connect

    Grin, A.; Smegal, J.; Lstiburek, J.

    2013-10-01

    Unvented roof strategies with open cell and closed cell spray polyurethane foam insulation sprayed to the underside of roof sheathing have been used since the mid-1990's to provide durable and efficient building enclosures. However, there have been isolated moisture related incidents reported anecdotally that raise potential concerns about the overall hygrothermal performance of these systems. This project involved hygrothermal modeling of a range of rainwater leakage and field evaluations of in-service residential roofs using spray foam insulation. All of the roof assemblies modeled exhibited drying capacity to handle minor rainwater leakage. All field evaluation locations of in-service residential roofs had moisture contents well within the safe range for wood-based sheathing. Explorations of eleven in-service roof systems were completed. The exploration involved taking a sample of spray foam from the underside of the roof sheathing, exposing the sheathing, then taking a moisture content reading. All locations had moisture contents well within the safe range for wood-based sheathing. One full-roof failure was reviewed, as an industry partner was involved with replacing structurally failed roof sheathing. In this case the manufacturer's investigation report concluded that the spray foam was installed on wet OSB based on the observation that the spray foam did not adhere well to the substrate and the pore structure of the closed cell spray foam at the ccSPF/OSB interface was indicative of a wet substrate.

  17. Characterization of Peripheral Nerve Sheath Tumors with 3T Proton MR Spectroscopy

    PubMed Central

    Fayad, L.M.; Wang, X.; Blakeley, J.O.; Durand, D.J.; Jacobs, M.A.; Demehri, S.; Subhawong, T.K.; Soldatos, T.; Barker, P.B.

    2014-01-01

    Background and Purpose The characterization of peripheral nerve sheath tumors is challenging. The purpose here was to investigate the diagnostic value of quantitative proton MR spectroscopy at 3T for the characterization of peripheral nerve sheath tumors as benign or malignant, compared with PET. Materials and Methods Twenty participants with 24 peripheral nerve sheath tumors underwent MR spectroscopy by use of a point-resolved sequence (TE, 135 ms). Six voxels were placed in 4 histologically proven malignant peripheral nerve sheath tumors and 22 voxels in 20 benign peripheral nerve sheath tumors (9 histologically proven, 11 with documented stability). The presence or absence of a trimethylamine signal was evaluated, the trimethylamine concentration estimated by use of phantom replacement methodology, and the trimethylamine fraction relative to Cr measured. MR spectroscopy results for benign and malignant peripheral nerve sheath tumors were compared by use of a Mann-Whitney test, and concordance or discordance with PET findings was recorded. Results In all malignant tumors and in 9 of 18 benign peripheral nerve sheath tumors, a trimethylamine peak was detected, offering the presence of trimethylamine as a sensitive (100%), but not specific (50%), marker of malignant disease. Trimethylamine concentrations (2.2 ± 2.8 vs 6.6 ± 5.8 institutional units; P < .049) and the trimethylamine fraction (27 ± 42 vs 88 ± 22%; P < .012) were lower in benign than malignant peripheral nerve sheath tumors. A trimethylamine fraction threshold of 50% resulted in 100% sensitivity (95% CI, 58.0%–100%) and 72.2% (95% CI, 59.5%–75%) specificity for distinguishing benign from malignant disease. MR spectroscopy and PET results were concordant in 12 of 16 cases, (2 false-positive results for MR spectroscopy and PET each). Conclusions Quantitative measurement of trimethylamine concentration by use of MR spectroscopy is feasible in peripheral nerve sheath tumors and shows promise as a

  18. A smart core-sheath nanofiber that captures and releases red blood cells from the blood

    NASA Astrophysics Data System (ADS)

    Shi, Q.; Hou, J.; Zhao, C.; Xin, Z.; Jin, J.; Li, C.; Wong, S.-C.; Yin, J.

    2016-01-01

    A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from

  19. Fractionated Stereotactic Radiotherapy in Patients With Optic Nerve Sheath Meningioma

    SciTech Connect

    Paulsen, Frank; Doerr, Stefan; Wilhelm, Helmut; Becker, Gerd; Bamberg, Michael; Classen, Johannes

    2012-02-01

    Purpose: To evaluate the effectiveness of fractionated stereotactic radiotherapy (SFRT) in the treatment of optic nerve sheath meningioma (ONSM). Methods and Materials: Between 1993 and 2005, 109 patients (113 eyes) with primary (n = 37) or secondary (n = 76) ONSM were treated according to a prospective protocol with SFRT to a median dose of 54 Gy. All patients underwent radiographic, ophthalmologic, and endocrine analysis before and after SFRT. Radiographic response, visual control, and late side effects were endpoints of the analysis. Results: Median time to last clinical, radiographic, and ophthalmologic follow up was 30.2 months (n = 113), 42.7 months (n = 108), and 53.7 months (n = 91), respectively. Regression of the tumor was observed in 5 eyes and progression in 4 eyes, whereas 104 remained stable. Visual acuity improved in 12, deteriorated in 11, and remained stable in 68 eyes. Mean visual field defects reduced from 33.6% (n = 90) to 17.8% (n = 56) in ipsilateral and from 10% (n = 94) to 6.7% (n = 62) in contralateral eyes. Ocular motility improved in 23, remained stable in 65, and deteriorated in 3 eyes. Radiographic tumor control was 100% at 3 years and 98% at 5 years. Visual acuity was preserved in 94.8% after 3 years and in 90.9% after 5 years. Endocrine function was normal in 90.8% after 3 years and in 81.3% after 5 years. Conclusions: SFRT represents a highly effective treatment for ONSM. Interdisciplinary counseling of the patients is recommended. Because of the high rate of preservation of visual acuity we consider SFRT the standard approach for the treatment of ONSM. Prolonged observation is warranted to more accurately assess late visual impairment. Moderate de-escalation of the radiation dose might improve the preservation of visual acuity and pituitary gland function.

  20. The research and preparation of a bi-layer biodegradable external sheath with directional drug release profiles for vein graft

    NASA Astrophysics Data System (ADS)

    Liu, Zhenjie; Guo, Zhenying; Si, Yi; Zhang, Xiangman; Shi, Zhenyu; Chen, Feng; Fu, Weiguo

    2013-11-01

    External sheath has been suggested for autologous vein grafts to inhibit neointimal hyperplasia and prevent anastomosis stricture. In this study, we prepared a bi-layer biodegradable paclitaxel-loaded sheaths with a synthetic copolymer poly(ethylene carbonate-ɛ-caprolactone) at room temperature. The bi-layer drug release profiles of the Paclitaxel-loaded (PTX-loaded) sheath significantly slow down the paclitaxel (PTX) release rates and result in a directional drug release way. Moreover, the nanofibrous layer of PTX-loaded poly(EC-CL) sheaths reduced the cytotoxicity and provided a better support for fibroblast adhesion and proliferation than the PTX-loaded layer of the sheaths. Thus, this study demonstrates that the bi-layer PTX-loaded poly(EC-CL) sheath with directional drug release profiles have a promising application for vein graft to against neointimal hyperplasia and anastomotic stricture.

  1. Grain growth behavior of Pb-Cu-Te cable sheathing alloys

    SciTech Connect

    Sahay, S.S.; Guruswamy, S.; Goodwin, F.

    1995-04-01

    Lead alloys are extensively used as sheathing material for power and telecommunication cables. Excellent extrusion properties, high ductility, extremely low recrystallization temperature, good fatigue and creep resistance, make these alloys ideal for cable sheathing application. Though the thickness of the lead sheath is only a few hundred {mu}m, it is a critical component of the cable. The lead layer in the cable is often the limiting factor both during the cable production and during its service phase. Up to several hundred miles of long single piece cables may be required for underground and underwater cables. Cracking in the lead sheath during the cable sheathing extrusion limits the production of such long cables while cracking of the lead sheath due to repeated vibration, creep and recrystallization limits the service life of these cables. The purpose of the present research is to increase the duration of cable extrusion time without compromising sheath integrity by minimizing deleterious precipitate formation and growth. Concentrations of Cu and Te in the commercial alloy are too small to contribute to precipitation strengthening. Therefore their positive influence on mechanical strength should mainly result from the influence of Cu and Te in solution on interdiffusivity and grain boundary mobility. The formation of large precipitates observed in Pb-Cu-Te alloys can be minimized and extrusion times increased without negatively affecting mechanical properties if the solute content is reduced to near solid solubility levels. In order to examine the effect of lowering solute content on microstructural stability and mechanical properties, compressive stress-strain behavior of a Pb-50 wt ppm Cu-100 wt ppm Te alloy with solute contents close to the solubility limits and a Pb-400 wt ppm Cu-400 wt ppm Te alloy was examined at room temperature. The grain growth kinetics in these alloys were studied in a temperature range of 100 to 225 C.

  2. Characterization of novel, phenol-soluble polypeptides which confer rigidity to the sheath of Methanospirillum hungatei GP1.

    PubMed Central

    Southam, G; Beveridge, T J

    1992-01-01

    Treatment of the Methanospirillum hungatei GP1 sheath with 90% (wt/vol) phenol resulted in the solubilization of a novel phenol-soluble group of polypeptides. These polypeptides were purified by the removal of insoluble material by ultracentrifugation and represented approximately 19% of the mass of the sheath. The phenol-insoluble material resembled untreated sheath but had lost its rigidity and cylindrical form. Recombination of phenol-soluble and phenol-insoluble fractions by dialysis to remove phenol resulted in cylindrical reassembly products. Although bona fide sheath (complete with the 2.8-nm lattice) was not produced, a role for the phenol-soluble polypeptides in the maintenance of sheath rigidity is implied. The phenol-soluble polypeptides have limited surface exposure as detected by antibodies on intact sheath; therefore, they are not responsible for the 2.8-nm repeat occurring on the outer face of the sheath. However, longitudinal and transverse linear labeling by protein A-colloidal gold on the outer and inner faces, respectively, occurred with monoclonal antibodies specific to the phenol-soluble polypeptides. Restricted surface exposure of phenol-soluble polypeptides on the sheath highlighted molecular defects in sheath architecture. These lattice faults may indicate sites of sheath growth to accommodate cell growth or division (longitudinal immunogold label) and filament division (transverse immunogold label). The identification of a second group of polypeptides within the infrastructure of the sheath suggests that the sheath is a trilaminar structure in which phenol-soluble polypeptides are sandwiched between sodium dodecyl sulfate-beta-mercaptoethanol-EDTA-soluble polypeptides (G. Southam and T. J. Beveridge, J. Bacteriol. 173:6213-6222, 1991) (phenol-insoluble material). Images PMID:1732226

  3. Transvenous Coil Embolization for Dural Arteriovenous Fistulas of the Ophthalmic Sheath: Report of Two Cases and Review of the Literature

    PubMed Central

    Hwang, Juyoung; Jo, Kyung-Il; Yeon, Je Young; Hong, Seung-Chyul

    2016-01-01

    We present two patients with a dural arteriovenous fistula (dAVF) of the ophthalmic sheath who developed progressive exophthalmos, conjunctival chemosis, and visual loss. These symptoms mimic those of cavernous sinus dAVFs. Dural AVFs of the ophthalmic sheath are extremely rare and their clinical management is controversial. We successfully treated these two patients by transvenous coil embolization. Transvenous embolization appears to be a safe and effective method to treat dAVFs of the ophthalmic sheath.

  4. Evolution of Piled-up Compressions in Modeled Coronal Mass Ejection Sheaths and the Resulting Sheath Structures

    NASA Astrophysics Data System (ADS)

    Das, Indrajit; Opher, Merav; Evans, Rebekah; Loesch, Cristiane; Gombosi, Tamas I.

    2011-03-01

    We study coronal mass ejection (CME)-driven shocks and the resulting post-shock structures in the lower corona (2-7 R sun). Two CMEs are erupted by modified Titov-Démoulin (TD) and Gibson-Low (GL) type flux ropes (FRs) with the Space Weather Modeling Framework. We observe a substantial pile-up of density compression and a narrow region of plasma depletion layer (PDL) in the simulations. As the CME/FR moves and expands in the solar wind medium, it pushes the magnetized material lying ahead of it. Hence, the magnetic field lines draping around the CME front are compressed in the sheath just ahead of the CME. These compressed field lines squeeze out the plasma sideways, forming PDL in the region. Solar plasma being pushed and displaced from behind forms a strong piled-up compression (PUC) of density downstream of the PDL. Both CMEs have comparable propagation speeds, while GL has larger expansion speed than TD due to its higher initial magnetic pressure. We argue that high CME expansion speed along with high solar wind density in the region is responsible for the large PUC found in the lower corona. In case of GL, the PUC is much wider, although the density compression ratio for both the cases is comparable. Although these simulations artificially initiate out-of-equilibrium CMEs and drive them in an artificial solar wind solution, we predict that PUCs, in general, will be large in the lower corona. This should affect the ion profiles of the accelerated solar energetic particles.

  5. Quantitative modeling of ICRF antennas with integrated time domain RF sheath and plasma physics

    SciTech Connect

    Smithe, David N.; D'Ippolito, Daniel A.; Myra, James R.

    2014-02-12

    Significant efforts have been made to quantitatively benchmark the sheath sub-grid model used in our time-domain simulations of plasma-immersed antenna near fields, which includes highly detailed three-dimensional geometry, the presence of the slow wave, and the non-linear evolution of the sheath potential. We present both our quantitative benchmarking strategy, and results for the ITER antenna configuration, including detailed maps of electric field, and sheath potential along the entire antenna structure. Our method is based upon a time-domain linear plasma model, using the finite-difference electromagnetic Vorpal/Vsim software. This model has been augmented with a non-linear rf-sheath sub-grid model, which provides a self-consistent boundary condition for plasma current where it exists in proximity to metallic surfaces. Very early, this algorithm was designed and demonstrated to work on very complicated three-dimensional geometry, derived from CAD or other complex description of actual hardware, including ITER antennas. Initial work with the simulation model has also provided a confirmation of the existence of propagating slow waves in the low density edge region, which can significantly impact the strength of the rf-sheath potential, which is thought to contribute to impurity generation. Our sheath algorithm is based upon per-point lumped-circuit parameters for which we have estimates and general understanding, but which allow for some tuning and fitting. We are now engaged in a careful benchmarking of the algorithm against known analytic models and existing computational techniques to insure that the predictions of rf-sheath voltage are quantitatively consistent and believable, especially where slow waves share in the field with the fast wave. Currently in progress, an addition to the plasma force response accounting for the sheath potential, should enable the modeling of sheath plasma waves, a predicted additional root to the dispersion, existing at the

  6. Biomechanics of the Optic Nerve Sheath in VIIP Syndrome

    NASA Technical Reports Server (NTRS)

    Ethier, C. Ross; Raykin, Julia; Gleason, Rudy; Mulugeta, Lealem; Myers, Jerry; Nelson, Emily; Samuels, Brian C.

    2014-01-01

    Long-duration space flight carries the risk of developing Visual Impairment and Intracranial Pressure (VIIP) syndrome, a spectrum of ophthalmic changes including posterior globe flattening, choroidal folds, distension of the optic nerve sheath (ONS), optic nerve kinking and potentially permanent degradation of visual function. The slow onset of VIIP, its chronic nature, and certain clinical features strongly suggest that biomechanical factors acting on the ONS play a role in VIIP. Here we measure several relevant ONS properties needed to model VIIP biomechanics. The ONS (meninges) of fresh porcine eyes (n7) was reflected, the nerve proper was truncated near the sclera, and the meninges were repositioned to create a hollow cylinder of meningeal connective tissue attached to the posterior sclera. The distal end was cannulated, sealed, and pressure clamped (mimicking cerebrospinal fluid [CSF] pressure), while the eye was also cannulated for independent control of intraocular pressure (IOP). The meninges were inflated (CSF pressure cycling 7-50 mmHg) while ONS outer diameter was imaged. In another set of experiments (n4), fluid permeation rate across the meninges was recorded by observing the drainage of an elevated fluid reservoir (30 mmHg) connected to the meninges. The ONS showed behavior typical of soft tissues: viscoelasticity, with hysteresis in early preconditioning cycles and repeatable behavior after 4 cycles, and nonlinear stiffening, particularly at CSF pressures 15 mmHg (Figure). Tangent moduli measured from the loading curve were 372 101, 1199 358, and 2050 379 kPa (mean SEM) at CSF pressures of 7, 15 and 30 mmHg, respectively. Flow rate measurements through the intact meninges at 30mmHg gave a permeability of 1.34 0.46 lmincm2mmHg (mean SEM). The ONS is a tough, strain-stiffening connective tissue that is surprisingly permeable. The latter observation suggests that there could be significant CSF drainage through the ONS into the orbit, likely important

  7. Optic Nerve Sheath Mechanics and Permeability in VIIP Syndrome

    NASA Technical Reports Server (NTRS)

    Raykin, Julia; Best, Lauren; Gleason, Rudy; Mulugeta, Lealem; Myers, Jerry; Nelson, Emily; Samuels, Brian C.; Ethier, C. R.

    2014-01-01

    Long-duration space flight carries the risk of developing Visual Impairment and Intracranial Pressure (VIIP) syndrome, a spectrum of ophthalmic changes including posterior globe flattening, choroidal folds, distension of the optic nerve sheath (ONS), optic nerve kinking and potentially permanent degradation of visual function. The slow onset of VIIP, its chronic nature, and certain clinical features strongly suggest that biomechanical factors acting on the ONS play a role in VIIP. Here we measure several relevant ONS properties needed to model VIIP biomechanics. The ONS (meninges) of fresh porcine eyes (n7) was reflected, the nerve proper was truncated near the sclera, and the meninges were repositioned to create a hollow cylinder of meningeal connective tissue attached to the posterior sclera. The distal end was cannulated, sealed, and pressure clamped (mimicking cerebrospinal fluid [CSF] pressure), while the eye was also cannulated for independent control of intraocular pressure (IOP). The meninges were inflated (CSF pressure cycling 7-50 mmHg) while ONS outer diameter was imaged. In another set of experiments (n4), fluid permeation rate across the meninges was recorded by observing the drainage of an elevated fluid reservoir (30 mmHg) connected to the meninges. The ONS showed behavior typical of soft tissues: viscoelasticity, with hysteresis in early preconditioning cycles and repeatable behavior after 4 cycles, and nonlinear stiffening, particularly at CSF pressures 15 mmHg (Figure). Tangent moduli measured from the loading curve were 372 101, 1199 358, and 2050 379 kPa (mean SEM) at CSF pressures of 7, 15 and 30 mmHg, respectively. Flow rate measurements through the intact meninges at 30mmHg gave a permeability of 1.34 0.46 lmincm2mmHg (mean SEM). The ONS is a tough, strain-stiffening connective tissue that is surprisingly permeable. The latter observation suggests that there could be significant CSF drainage through the ONS into the orbit, likely important

  8. Elongation growth of the leaf sheath base of Avena sativa seedlings: regulation by hormones and sucrose

    NASA Technical Reports Server (NTRS)

    Brock, T. G.; Kaufman, P. B.

    1991-01-01

    The leaf sheath base of the seedling of Avena sativa was characterized for growth response to hormones and sucrose. Six day old plants, raised under a 10:14 hr light:dark cycle, were excised at the coleoptilar node and 1 cm above the node for treatment. The growth of the leaf sheath base was promoted by gibberellic acid (GA3) and this response was dose dependent. The lag to response initiation was approximately 4 hr. Growth with or without GA3 (10 micromoles) was transient, diminishing appreciably after 48 hr. The addition of 10 mM sucrose greatly prolonged growth; the effect of GA3 and sucrose was additive. Neither indole-3-acetic acid (IAA) nor the cytokinin N6-benzyladenine (BA), alone or in combination, promoted the growth of leaf sheath bases. However, both significantly inhibited the action of GA3. The inhibitory effect of IAA was dose dependent and was not affected by the addition of BA or sucrose. These results indicate that the growth of leaf sheath bases of Avena sativa is promoted specifically by gibberellin, that this action depends on the availability of carbohydrates from outside of the leaf sheath base, and that the promotional effect of GA3 can be modified by either auxins or cytokinins.

  9. Effect of the q-nonextensive electron velocity distribution on a magnetized plasma sheath

    SciTech Connect

    Safa, N. Navab Ghomi, H.; Niknam, A. R.

    2014-08-15

    In this work, a sheath model has been developed to investigate the effect of the q-nonextensive electron velocity distribution on the different characteristics of a magnetized plasma. By using Segdeev potential method, a modified Bohm criterion for a magnetized plasma with the nonextensive electron velocity distribution is derived. The sheath model is then used to analyze numerically the sheath structure under different q, the parameter quantifying the nonextensivity degree of the system. The results show that as the q-parameter decreases, the floating potential becomes more negative. The sheath length increases at the lower values of the q-parameter due to the increase in the electron population at the high-energy tail of the distribution function. As q-parameter decreases, the effective temperature of the electrons increases which results in a more extended plasma sheath. The ion velocity and density profiles for the different nonextensivity degrees of the system reflect the gyro-motion of the ions in the presence of the magnetic field. Furthermore, the results coincide with those given by the Maxwellian electron distribution function, when q tends to 1.

  10. Fully kinetic model of breakdown during sheath expansion after interruption of vacuum arcs

    NASA Astrophysics Data System (ADS)

    Wang, Zhenxing; Wang, Haoran; Zhou, Zhipeng; Tian, Yunbo; Geng, Yingsan; Wang, Jianhua; Liu, Zhiyuan

    2016-08-01

    Research on sheath expansion is critical to the understanding of the dielectric recovery process in a vacuum interrupter after interruption of vacuum arcs. In this paper, we investigated how residual plasma affects breakdown in the sheath expansion period after the current zero. To simulate sheath expansion and breakdown, we developed a fully kinetic particle-in-cell Monte Carlo collision model with one spatial dimension and three velocity dimensions. The model accounted for various collisions, including ionization, excitation, elastic collisions, charge exchange, and momentum exchange, and we added an external circuit to the model to make the calculations self-consistent. The existence of metal vapor slowed the sheath expansion in the gap and caused high electric field formation in front of the cathode surface. The initial residual plasma, which was at sufficiently low density, seemed to have a limited impact on breakdown, and the metal vapor dominated the breakdown in this case. Additionally, the breakdown probability was sensitive to the initial plasma density if the value exceeded a specific threshold, and plasma at sufficiently high density could mean that breakdown would occur more easily. We found that if the simulation does not take the residual plasma into account, it could overestimate the critical value of the metal vapor density, which is always used to describe the boundary of breakdown after interruption of vacuum arcs. We discussed the breakdown mechanism in sheath expansion, and the breakdown is determined by a combination of metal vapor, residual plasma, and the electric field in front of the cathode surface.

  11. Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

    SciTech Connect

    Křivská, A.; Colas, L.; Milanesio, D.

    2015-12-10

    Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.

  12. Particulates from Hydrophilic-Coated Guiding Sheaths Embolize to the Brain

    PubMed Central

    Stanley, James R.L.; Tzafriri, Abraham R.; Regan, Kathryn; LaRochelle, Alan; Wong, Gee; Zani, Brett G.; Markham, Peter M.; Bailey, Lynn; Spognardi, Anna; Kopia, Gregory A.; Edelman, Elazer R.

    2015-01-01

    Aims We sought to evaluate the incidence of embolic material in porcine brain following vascular interventions using hydrophilic-coated sheaths. Methods and results A new self-expanding stent and delivery system (SDS) were deployed through a hydrophilic-coated (Cook® Flexor Ansel) Guiding Sheath into iliac and/or carotid arteries of 23 anesthetized Yucatan miniswine. Animals were euthanized at 3, 30, 90 and 180 days and brains were removed for histological analysis. In an additional single control animal, the guiding sheath was advanced but no SDS was deployed. Advancement of the coated guiding sheath with or without the SDS was associated with frequent foreign material in the arterioles of the brain. The embolic material was amorphous, non-refractile, non-crystalline, and non-birefringent and typically lightly basophilic with a slight stippled appearance on hematoxylin and eosin (H&E) stain. Material was observed at all time points involving 54% of all study animals (ie, test and control) and in vitro after incubation in 0.9% saline. Conclusions The hydrophilic coating on a clinically used guiding sheath readily avulses and embolizes to the brain during deployment in a porcine model. Further documentation of this effect and monitoring in clinical scenarios is warranted. PMID:25735934

  13. Properties of in situ made MgB2 in Nb or Ti sheath

    NASA Astrophysics Data System (ADS)

    Kováč, P.; Hušek, I.; Kopera, L.; Melišek, T.; Rosová, A.; Dobročka, E.

    2013-02-01

    Pure Nb and Ti have been used as sheath materials for MgB2 wires examined experimentally. The reason for this research is to compare the effects of these metallic sheaths on the basic properties of MgB2 superconductor. Single-core SiC doped MgB2 wires with Nb and/or Ti sheaths have been made by a powder-in-tube in situ process. Different transport currents, phase compositions and grain connectivity were observed for Nb- and Ti sheathed MgB2 heat treated at temperatures 650-850 °C/30 min. It was found that the critical current density of MgB2/Nb annealed above 700 °C rapidly decreases, while Jc of MgB2/Ti is systematically increasing with temperature. This is explained by the positive role of Ti absorbing impurities from the MgB2 core and by the negative effect of boron diffusion into Nb, reducing the quantity and worsening the quality of the MgB2 core. The obtained results show clearly that a Ti sheath offers the application of higher heat treatment temperatures (above 700 °C) and consequently the achievement of higher critical current densities in comparison to MgB2/Nb.

  14. The structural sheath protein of aphids is required for phloem feeding.

    PubMed

    Will, Torsten; Vilcinskas, Andreas

    2015-02-01

    Aphids produce two types of saliva that mediate their interactions with plants. Watery saliva is secreted during cell penetration and ingestion, whereas gel saliva is secreted during stylet movement through the apoplast where it forms a sheath around the stylet to facilitate penetration and seal puncture sites on cell membranes. In order to study the function of the sheath when aphids interact with plants, we used RNA interference (RNAi) to silence the aphid structural sheath protein (SHP) in the pea aphid Acyrthosiphon pisum. The injection of 50 ng of double stranded RNA completely disrupted sheath formation, as confirmed by scanning electron microscopy. Aphid behavior was monitored using the electrical penetration graph technique, revealing that disrupted sheath formation prevented efficient long-term feeding from sieve tubes, with a silencing effect on reproduction but not survival. We propose that sealing the stylet penetration site in the sieve tube plasma membrane is part of a two-step mechanism to suppress sieve-tube occlusion by preventing calcium influx into the sieve tube lumen. The SHP is present in several aphid species and silencing has a similar impact to aphid-resistant plants, suggesting that SHP is an excellent target for RNAi-mediated pest control.

  15. 3D Relativistic Magnetohydrodynamic Simulations of Magnetized Spine-Sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Hardee, Philip; Nishikawa, Ken-Ichi

    2006-01-01

    Numerical simulations of weakly magnetized and strongly magnetized relativistic jets embedded in a weakly magnetized and strongly magnetized stationary or weakly relativistic (v = c/2) sheath have been performed. A magnetic field parallel to the flow is used in these simulations performed by the new GRMHD numerical code RAISHIN used in its RMHD configuration. In the numerical simulations the Lorentz factor gamma = 2.5 jet is precessed to break the initial equilibrium configuration. In the simulations sound speeds are less than or equal to c/the square root of 3 in the weakly magnetized simulations and less than or equal to 0.56 c in the strongly magnetized simulations. The Alfven wave speed is less than or equal to 0.07 c in the weakly magnetized simulations and less than or equal to 0.56 c in the strongly magnetized simulations. The results of the numerical simulations are compared to theoretical predictions from a normal mode analysis of the linearized relativistic magnetohydrodynamic (RMHD) equations capable of describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized relativistically moving sheath. The theoretical dispersion relation allows investigation of effects associated with maximum possible sound speeds, Alfven wave speeds near light speed and relativistic sheath speeds. The prediction of increased stability of the weakly magnetized system resulting from c/2 sheath speeds and the stabilization of the strongly magnetized system resulting from c/2 sheath speeds is verified by the numerical simulation results.

  16. Modeling of Sheath Ion-Molecule Reactions in Plasma Enhanced Chemical Vapor Deposition of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Hash, David B.; Govindan, T. R.; Meyyappan, M.

    2004-01-01

    In many plasma simulations, ion-molecule reactions are modeled using ion energy independent reaction rate coefficients that are taken from low temperature selected-ion flow tube experiments. Only exothermic or nearly thermoneutral reactions are considered. This is appropriate for plasma applications such as high-density plasma sources in which sheaths are collisionless and ion temperatures 111 the bulk p!asma do not deviate significantly from the gas temperature. However, for applications at high pressure and large sheath voltages, this assumption does not hold as the sheaths are collisional and ions gain significant energy in the sheaths from Joule heating. Ion temperatures and thus reaction rates vary significantly across the discharge, and endothermic reactions become important in the sheaths. One such application is plasma enhanced chemical vapor deposition of carbon nanotubes in which dc discharges are struck at pressures between 1-20 Torr with applied voltages in the range of 500-700 V. The present work investigates The importance of the inclusion of ion energy dependent ion-molecule reaction rates and the role of collision induced dissociation in generating radicals from the feedstock used in carbon nanotube growth.

  17. Plasma sheath properties in a magnetic field parallel to the wall

    NASA Astrophysics Data System (ADS)

    Moritz, J.; Faudot, E.; Devaux, S.; Heuraux, S.

    2016-06-01

    Particle in cell simulations were carried out with a plasma bounded by two absorbing walls and a magnetic field applied parallel to them. Both the sheath extent and the potential drop in it were derived from simulations for different plasma parameters, such as the electron and ion temperature Ti, particle density, and ion mass. Both of them exhibit a power law dependent on the Larmor to plasma ion pulsation ratio Ωi. For increasing values of the magnetic field, the potential drop within the sheath decreases from a few Ti/e down to zero, where e stands for the electron charge. The space charge extent increases with Ωi and saturates to 2.15 ion Larmor radius. A simple model of sheath formation in such a magnetic field configuration is presented. Assuming strongly magnetized electrons, and neglecting collisions and ionizations, a new typical length is evidenced, which depends on the ratio Ωi. The charge separation sheath width is theoretically found to increase from a combination of the electron gyroradius and the ion Debye length for low Ωi ratios up to several ion gyroradii for strongly magnetized ions. Both the calculated sheath extent and plasma potential show a fair agreement with the numerical simulations.

  18. Observation of an electron sheath at a large, transiently biassed surface in the GEC cell

    NASA Astrophysics Data System (ADS)

    Barroy, P. R. J.; Goodyear, A.; Braithwaite, N. St. J.

    2001-10-01

    Sheath reversal has been investigated in front of a biassed surface embedded into the ground electrode of a capacitively coupled GEC cell. Radio frequency bursts (several tens of volts amplitude) were applied to the surface (20 mm diameter including guard ring) and fast, two dimensional observations made of the light emission using an intensified CCD camera synchronously gated within the succession of bursts. A guard ring, biassed to the same potential, ensures sheath planarity. The evolution of the optical emission has been followed during the dc biassing period. If the applied RF is large enough and the timescale short enough a perturbation of the plasma sheath is observed. At the onset of the RF burst periodic, sheath reversal is achieved as the potential of the surface exceeds that of the plasma. After several cycles of RF, the surface acquires enough negative charge to bias itself negatively, below plasma potential; sheath reversal then stops. The overall effect is accompanied by light emision from species excited by electrons accelerated towards the surface. Modelling of the phenomenon has been conducted to account for the observations.

  19. Sheath structure in plasma with two species of positive ions and secondary electrons

    NASA Astrophysics Data System (ADS)

    Xiao-Yun, Zhao; Nong, Xiang; Jing, Ou; De-Hui, Li; Bin-Bin, Lin

    2016-02-01

    The properties of a collisionless plasma sheath are investigated by using a fluid model in which two species of positive ions and secondary electrons are taken into account. It is shown that the positive ion speeds at the sheath edge increase with secondary electron emission (SEE) coefficient, and the sheath structure is affected by the interplay between the two species of positive ions and secondary electrons. The critical SEE coefficients and the sheath widths depend strongly on the positive ion charge number, mass and concentration in the cases with and without SEE. In addition, ion kinetic energy flux to the wall and the impact of positive ion species on secondary electron density at the sheath edge are also discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11475220 and 11405208), the Program of Fusion Reactor Physics and Digital Tokamak with the CAS “One-Three-Five” Strategic Planning, the National ITER Program of China (Grant No. 2015GB101003), and the Higher Education Natural Science Research Project of Anhui Province, China (Grant No. 2015KJ009).

  20. Support of Nerve Conduction by Respiring Myelin Sheath: Role of Connexons.

    PubMed

    Ravera, Silvia; Bartolucci, Martina; Adriano, Enrico; Garbati, Patrizia; Ferrando, Sara; Ramoino, Paola; Calzia, Daniela; Morelli, Alessandro; Balestrino, Maurizio; Panfoli, Isabella

    2016-05-01

    Recently, we have demonstrated that myelin conducts an extramitochondrial oxidative phosphorylation, hypothesizing a novel supportive role for myelin in favor of the axon. We have also hypothesized that the ATP produced in myelin could be transferred thought gap junctions. In this work, by biochemical, immunohistochemical, and electrophysiological techniques, the existence of a connection among myelin to the axon was evaluated, to understand how ATP could be transferred from sheath to the axoplasm. Data confirm a functional expression of oxidative phosphorylation in isolated myelin. Moreover, WB and immunohistochemistry on optic nerve slices show that connexins 32 and 43 are present in myelin and colocalize with myelin basic protein. Interestingly, addition of carbenoxolone or oleamide, two gap junction blockers, causes a decrease in oxidative metabolism in purified myelin, but not in mitochondria. Similar effects were observed on conduction speed in hippocampal Schaffer collateral, in the presence of oleamide. Confocal analysis of optic nerve slices showed that lucifer yellow (that only passes through aqueous pores) signal was found in both the sheath layers and the axoplasma. In the presence of oleamide, but not with oleic acid, signal significantly decreased in the sheath and was lost inside the axon. This suggests the existence of a link among myelin and axons. These results, while supporting the idea that ATP aerobically synthesized in myelin sheath could be transferred to the axoplasm through gap junctions, shed new light on the function of the sheath.

  1. Analysis of Particle Detectors in Plasma Sheaths on Sounding Rockets and in Laboratory Plasmas

    NASA Astrophysics Data System (ADS)

    Fisher, Lisa; Lynch, Kristina

    2013-10-01

    The influence of plasma sheaths on particle measurements is a well-known problem. Improvements in computational speed and memory have made the use of particle-in-cell codes, attainable on a laptop. These codes can calculate complex sheath structures and include most of the relevant physics. We will discuss how the use of one such code, SPIS, has been integrated into our data processing for the MICA sounding rocket. This inclusion of sheath physics has allowed us to describe the current-voltage signature of an ion retarding potential analyzer, called the PIP, to measure the ambient ionospheric temperature, as well as to examine the possibility of ion upflow. These results will be compared with the other instrumentation on MICA, which use traditional thin-sheath approximations. This comparison will emphasize the strengths and weaknesses of these other data analysis methods and call attention to the need to include sheath physics when measuring very low energy populations. Additionally, these instruments have also been tested in the Dartmouth College plasma facility. This provides another set of plasma conditions for testing and extrapolating our method to a future low-orbit mission.

  2. Numerical study of an electrostatic plasma sheath containing two species of charged dust particles

    SciTech Connect

    Foroutan, G.; Akhoundi, A.

    2012-10-01

    A multi-fluid model is used to study the dynamics of a dusty plasma sheath consists of electrons, ions, and two species of charged dust particles, i.e., nano-size and micron-size particles. It is found that, when the sheath is dominated by the nano-size dust grains, spatially periodic fluctuations are developed in the profiles of the sheath potential, and the number density and velocity of the plasma and dust particles. Due to inertial effects, the fluctuations in the parameters of the micron-size grains are much lower than those of the other parameters. The competition between the electric and ion drag forces plays the primary role in development of the fluctuations. The spatial period of the fluctuations is approximately a few Debye lengths and their amplitude depends on the plasma and dust parameters. The fluctuations are reduced by the increase in the radius, mass density, and Mach number of the nano-size particles, as well as the density and Mach number of the ions. But, they are enhanced by the increase in the plasma number density and the electron temperature. The sheath thickness demonstrates a non-monotonic behavior against variation of the nanoparticle parameters, i.e., it first decreases quickly, shows a minimum, and then increases. However, the sheath width always decreases with the plasma number density and ion Mach number, while grows linearly with the electron temperature.

  3. Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

    NASA Astrophysics Data System (ADS)

    Křivská, A.; Bobkov, V.; Colas, L.; Jacquot, J.; Milanesio, D.; Ochoukov, R.

    2015-12-01

    Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performed during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.

  4. Electromagnetic induction between axons and their schwann cell myelin-protein sheaths.

    PubMed

    Goodman, G; Bercovich, D

    2013-12-01

    Two concepts have long dominated vertebrate nerve electrophysiology: (a) Schwann cell-formed myelin sheaths separated by minute non-myelinated nodal gaps and spiraling around axons of peripheral motor nerves reduce current leakage during propagation of trains of axon action potentials; (b) "jumping" by action potentials between successive nodes greatly increases signal conduction velocity. Long-held and more recent assumptions and issues underlying those concepts have been obscured by research emphasis on axon-sheath biochemical symbiosis and nerve regeneration. We hypothesize: mutual electromagnetic induction in the axon-glial sheath association, is fundamental in signal conduction in peripheral and central myelinated axons, explains the g-ratio and is relevant to animal navigation.

  5. Disease-reducing effect of Chromolaena odorata extract on sheath blight and other rice diseases.

    PubMed

    Khoa, Nguyen Đac; Thuy, Phan Thi Hong; Thuy, Tran Thi Thu; Collinge, David B; Jørgensen, Hans Jørgen Lyngs

    2011-02-01

    Sheath blight caused by Rhizoctonia solani (teleomorph: Thanatephorus cucumeris) is a major cause of crop loss in intensive rice production systems. No economically viable control methods have been developed. We screened aqueous extracts of common herbal plants that could reduce sheath blight lesions and found that foliar spraying and seed soaking application of extracts of either fresh or dried leaves of Chromolaena odorata gave up to 68% reduction in sheath blight lesion lengths under controlled and semi-field conditions. The observed reductions were not dependent on growth conditions of C. odorata and rice cultivar. The effect was observed until 21 days after inoculation and was not dependent on microbial activity. Under semi-field conditions, extracts also reduced severity of other important rice diseases, i.e., blast (Pyricularia oryzae) using foliar spray (up to 45%), brown spot (Bipolaris oryzae) using seed treatment (up to 57%), and bacterial blight (Xanthomonas oryzae pv. oryzae) using both application methods (up to 50%).

  6. A matching approach to communicate through the plasma sheath surrounding a hypersonic vehicle

    SciTech Connect

    Gao, Xiaotian; Jiang, Binhao

    2015-06-21

    In order to overcome the communication blackout problem suffered by hypersonic vehicles, a matching approach has been proposed for the first time in this paper. It utilizes a double-positive (DPS) material layer surrounding a hypersonic vehicle antenna to match with the plasma sheath enclosing the vehicle. Analytical analysis and numerical results indicate a resonance between the matched layer and the plasma sheath will be formed to mitigate the blackout problem in some conditions. The calculated results present a perfect radiated performance of the antenna, when the match is exactly built between these two layers. The effects of the parameters of the plasma sheath have been researched by numerical methods. Based on these results, the proposed approach is easier to realize and more flexible to the varying radiated conditions in hypersonic flight comparing with other methods.

  7. Sheath oscillation characteristics and effect on near-wall conduction in a krypton Hall thruster

    SciTech Connect

    Zhang, Fengkui Kong, Lingyi; Li, Chenliang; Yang, Haiwei; Li, Wei

    2014-11-15

    Despite its affordability, the krypton Hall-effect thruster in applications always had problems in regard to performance. The reason for this degradation is studied from the perspective of the near-wall conductivity of electrons. Using the particle-in-cell method, the sheath oscillation characteristics and its effect on near-wall conduction are compared in the krypton and xenon Hall-effect thrusters both with wall material composed of BNSiO{sub 2}. Comparing these two thrusters, the sheath in the krypton-plasma thruster will oscillate at low electron temperatures. The near-wall conduction current is only produced by collisions between electrons and wall, thereby causing a deficiency in the channel current. The sheath displays spatial oscillations only at high electron temperature; electrons are then reflected to produce the non-oscillation conduction current needed for the krypton-plasma thruster. However, it is accompanied with intensified oscillations.

  8. STRETCHY ELECTRONICS. Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles.

    PubMed

    Liu, Z F; Fang, S; Moura, F A; Ding, J N; Jiang, N; Di, J; Zhang, M; Lepró, X; Galvão, D S; Haines, C S; Yuan, N Y; Yin, S G; Lee, D W; Wang, R; Wang, H Y; Lv, W; Dong, C; Zhang, R C; Chen, M J; Yin, Q; Chong, Y T; Zhang, R; Wang, X; Lima, M D; Ovalle-Robles, R; Qian, D; Lu, H; Baughman, R H

    2015-07-24

    Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson's ratio on torsional actuation and electronic properties. PMID:26206929

  9. Constrained sheath optics for high thrust density, low specific impulse ion thrusters

    NASA Technical Reports Server (NTRS)

    Wilbur, Paul J.; Han, Jian-Zhang

    1987-01-01

    The results of an experimental study showing that a contoured, fine wire mesh attached to the screen grid can be used to control the divergence characteristics of ion beamlets produced at low net-to-total accelerating voltage ratios are presented. The influence of free and constrained-sheath optics systems on beamlet divergence characteristics are found to be similar in the operating regime investigated, but it was found that constrained-sheath optics systems can be operated at higher perveance levels than free-sheath ones. The concept of a fine wire interference probe that can be used to study ion beamlet focusing behavior is introduced. This probe is used to demonstrate beamlet focusing to a diameter about one hundreth of the screen grid extraction aperture diameter. Additional testing is suggested to define an optimally contoured mesh that could yield well focused beamlets at net-to-total accelerating voltage ratios below about 0.1.

  10. Particle-in-cell study of the ion-to-electron sheath transition

    NASA Astrophysics Data System (ADS)

    Scheiner, Brett; Baalrud, Scott D.; Hopkins, Matthew M.; Yee, Benjamin T.; Barnat, Edward V.

    2016-08-01

    The form of a sheath near a small electrode, with bias changing from below to above the plasma potential, is studied using 2D particle-in-cell simulations. When the electrode is biased within Te/2 e below the plasma potential, the electron velocity distribution functions (EVDFs) exhibit a loss-cone type truncation due to fast electrons overcoming the small potential difference between the electrode and plasma. No sheath is present in this regime, and the plasma remains quasineutral up to the electrode. The EVDF truncation leads to a presheath-like density and flow velocity gradients. Once the bias exceeds the plasma potential, an electron sheath is present. In this case, the truncation driven behavior persists, but is accompanied by a shift in the maximum value of the EVDF that is not present in the negative bias cases. The flow moment has significant contributions from both the flow shift of the EVDF maximum, and the loss-cone truncation.

  11. Linkage between gravity perception and response in the grass leaf-sheath pulvinus

    NASA Technical Reports Server (NTRS)

    Dayanandan, P.; Franklin, C. I.; Kaufman, P. B.

    1982-01-01

    Cellulose synthesis inhibitors 2,6-dichlorobenzonitrile and coumarin inhibit the normal gravitropic response of the leaf-sheath pulvini in several grasses. These inhibitors induce thickenings that are mostly distributed in the radial walls. Their distribution patterns follow a previously published equation that describes the geometry of asymmetric growth in the leaf-sheath pulvinus. It is proposed that radial transport of growth promotors may account for the observed asymmetric growth rather than the classical concept of lateral downward transport in an horizontally placed shoot. Electron microscopic observation of an interaction between the tonoplast membrane and statoliths suggests that such an interaction might be a basis for gravity perception in grass leaf-sheath pulvini.

  12. Measurements of the asymmetric, dynamic sheath around a pulse biased sphere immersed in flowing metal plasma

    SciTech Connect

    Anders, Andre; Wu, Hongchen; Anders, Andre

    2008-06-13

    A long-probe technique was utilized to record the expansion and retreat of the dynamic sheath around a spherical substrate immersed in pulsed cathode arc metal plasma. Positively biased, long cylindrical probes were placed on the side and downstream of a negatively pulsed biased stainless steel sphere of 1" (25.4 mm) diameter. The amplitude and width of the negative high voltage pulses (HVP) were 2 kV, 5 kV, 10 kV, and 2 mu s, 4 mu s, 10 mu s, respectively. The variation of the probe (electron) current during the HVP is a direct measure for the sheath expansion and retreat. Maximum sheath sizes were determined for the different parameters of the HVP. The expected rarefaction zone behind the biased sphere (wake) due to the fast plasma flow was clearly established and quantified.

  13. Determination of the levitation limits of dust particles within the sheath in complex plasma experiments

    SciTech Connect

    Douglass, Angela; Land, Victor; Qiao Ke; Matthews, Lorin; Hyde, Truell

    2012-01-15

    Experiments are performed in which dust particles are levitated at varying heights above the powered electrode in a radio frequency plasma discharge by changing the discharge power. The trajectories of particles dropped from the top of the discharge chamber are used to reconstruct the vertical electric force acting on the particles. The resulting data, together with the results from a self-consistent fluid model, are used to determine the lower levitation limit for dust particles in the discharge and the approximate height above the lower electrode where quasineutrality is attained, locating the sheath edge. These results are then compared with current sheath models. It is also shown that particles levitated within a few electron Debye lengths of the sheath edge are located outside the linearly increasing portion of the electric field.

  14. Electromagnetic particle in cell modeling of the plasma focus: Current sheath formation and lift off

    SciTech Connect

    Seng, Y. S.; Lee, P.; Rawat, R. S.

    2014-02-15

    The shaping and formation of the current sheath takes place in the breakdown phase of a plasma focus device and critically controls the device performance. Electrostatic particle in cell codes, with magnetic effects ignored, have been used to model the breakdown phase. This Letter reports the successful development and implementation of an electromagnetic particle in cell (EMPIC) code, including magnetic effects self-consistently, to simulate the breakdown phase; from the ionization, localization and gliding discharge along the insulator to the time instant of current sheath lift off. The magnetic field was found to be appreciable from the time the current sheath came into contact with the anode with increased local current, initiating the voltage breakdown of the device as a result.

  15. Unified model of the rf plasma sheath: Part 2, Asymptotic connection formulae

    SciTech Connect

    Riley, M.E.

    1996-08-01

    A previously-developed approximation to the first integral of the Poisson equation enables one to obtain solutions for the voltage- current characteristics of a radio-frequency (rf) plasma sheath that are valid over the whole range of inertial response of the ions to an imposed rf voltage or current-specified conditions. The theory reproduced the time-dependent voltage-current characteristics of the two extreme cases corresponding to the Lieberman rf sheath theory and the Metze-Ernie-Oskam theory. In this paper the sheath model is connected to the plasma bulk description, and a prescription is given for the ion relaxation time constant, which determines the time-dependent ion impact energy on the electrode surface. It appears that this connected model should be applicable to those high density, low pressure plasmas in which the Debye length is a small fraction of the ion mean free path, which itself is a small fraction of the plasma dimension.

  16. STRETCHY ELECTRONICS. Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles.

    PubMed

    Liu, Z F; Fang, S; Moura, F A; Ding, J N; Jiang, N; Di, J; Zhang, M; Lepró, X; Galvão, D S; Haines, C S; Yuan, N Y; Yin, S G; Lee, D W; Wang, R; Wang, H Y; Lv, W; Dong, C; Zhang, R C; Chen, M J; Yin, Q; Chong, Y T; Zhang, R; Wang, X; Lima, M D; Ovalle-Robles, R; Qian, D; Lu, H; Baughman, R H

    2015-07-24

    Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson's ratio on torsional actuation and electronic properties.

  17. Hierarchically buckled sheath-core fibers for superelastic electronics, sensors, and muscles

    NASA Astrophysics Data System (ADS)

    Liu, Z. F.; Fang, S.; Moura, F. A.; Ding, J. N.; Jiang, N.; Di, J.; Zhang, M.; Lepró, X.; Galvão, D. S.; Haines, C. S.; Yuan, N. Y.; Yin, S. G.; Lee, D. W.; Wang, R.; Wang, H. Y.; Lv, W.; Dong, C.; Zhang, R. C.; Chen, M. J.; Yin, Q.; Chong, Y. T.; Zhang, R.; Wang, X.; Lima, M. D.; Ovalle-Robles, R.; Qian, D.; Lu, H.; Baughman, R. H.

    2015-07-01

    Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson’s ratio on torsional actuation and electronic properties.

  18. Magnetic Field Generation in Core-sheath Jets via the Kinetic Kelvin-Helmholtz Instability

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Hardee, P. E.; Duţan, I.; Niemiec, J.; Medvedev, M.; Mizuno, Y.; Meli, A.; Sol, H.; Zhang, B.; Pohl, M.; Hartmann, D. H.

    2014-09-01

    We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.

  19. Magnetic field generation in core-sheath jets via the kinetic Kelvin-Helmholtz instability

    SciTech Connect

    Nishikawa, K.-I.; Hardee, P. E.; Duţan, I.; Niemiec, J.; Medvedev, M.; Mizuno, Y.; Meli, A.; Sol, H.; Zhang, B.; Pohl, M.; Hartmann, D. H.

    2014-09-20

    We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.

  20. Disease-reducing effect of Chromolaena odorata extract on sheath blight and other rice diseases.

    PubMed

    Khoa, Nguyen Đac; Thuy, Phan Thi Hong; Thuy, Tran Thi Thu; Collinge, David B; Jørgensen, Hans Jørgen Lyngs

    2011-02-01

    Sheath blight caused by Rhizoctonia solani (teleomorph: Thanatephorus cucumeris) is a major cause of crop loss in intensive rice production systems. No economically viable control methods have been developed. We screened aqueous extracts of common herbal plants that could reduce sheath blight lesions and found that foliar spraying and seed soaking application of extracts of either fresh or dried leaves of Chromolaena odorata gave up to 68% reduction in sheath blight lesion lengths under controlled and semi-field conditions. The observed reductions were not dependent on growth conditions of C. odorata and rice cultivar. The effect was observed until 21 days after inoculation and was not dependent on microbial activity. Under semi-field conditions, extracts also reduced severity of other important rice diseases, i.e., blast (Pyricularia oryzae) using foliar spray (up to 45%), brown spot (Bipolaris oryzae) using seed treatment (up to 57%), and bacterial blight (Xanthomonas oryzae pv. oryzae) using both application methods (up to 50%). PMID:20839964

  1. Sheath effects observed on a 10 meter high voltage panel in simulated low earth orbit plasma

    NASA Technical Reports Server (NTRS)

    Mccox, J. E.; Konradi, A.

    1979-01-01

    A large (1m x 10m) flat surface of conductive material was biased to high voltage (+ or - 3000 V) to simulate the behavior of a large solar array in low earth orbit. The model array was operated in a plasma environment of 1,000 to 1,000,000/cu cm, with sufficient free space around it for the resulting plasma sheaths to develop unimpeded for 5-10 meters into the surrounding plasma. Measurements of the resulting sheath thickness were obtained. The observed thickness varied approximately as V to the 3/4 power and N to the 1/2 power. This effect appears to limit total current leakage from the test array until sheath dimensions exceed about 1 meter. Total leakage current was also measured with the array.

  2. Role of disulfide bonds in maintaining the structural integrity of the sheath of Leptothrix discophora SP-6.

    PubMed Central

    Emerson, D; Ghiorse, W C

    1993-01-01

    Isolated sheaths of Leptothrix discophora SP-6 (ATCC 51168) were tested for susceptibility to degradation by a variety of chemical denaturants and lytic enzymes and found to be resistant to many reagents and enzyme treatments. However, disulfide bond-reducing agents such as dithiothreitol (DTT), beta-mercaptoethanol, sodium cyanide, and sodium sulfite degraded the sheath, especially at elevated pH (pH 9) and temperature (50 degrees C). DTT and beta-mercaptoethanol caused more rapid degradation of the sheath than cyanide or sulfite. Treatment of the sheath with 1 N NaOH resulted in rapid breakdown, while treatment with 1 N HCl resulted in slow but significant hydrolysis. Transmission electron microscopy showed that the 6.5-nm fibrils previously shown to be an integral structural element of the sheath fabric (D. Emerson and W. C. Ghiorse, J. Bacteriol. 175:7808-7818, 1993) were progressively dissociated into random masses during DTT-induced degradation. Quantitation of disulfide bonds with DTT showed that the sheaths contained approximately 2.2 mumol of disulfides per mg of sheath protein. Reaction with 5,5'-dithio-bis-(2-nitrobenzoic acid) showed that sheaths also contained approximately 0.8 mumol of free sulfhydryls per mg of protein. A sulfhydryl-specific fluorescent probe (fluorescein 5-maleimide) showed that the free sulfhydryls in sheathed cell filaments were evenly distributed throughout the sheath. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis autoradiography of [14C]iodoacetamide-labeled sheaths and DTT-dissociated sheath fibril suspensions showed that the majority of 14C-labeled sulfhydryls in the sheaths did not enter the gel. However, low-molecular-mass silver-staining bands (14 to 45 kDa) did appear in the gels after iodoacetic acid or iodoacetamide alkylation of the dissociated fibrils. These bands did not stain with Coomassie blue. Their migration in gels was slightly affected by digestion with pronase. The fibrils contained 20 to 25

  3. Role of disulfide bonds in maintaining the structural integrity of the sheath of Leptothrix discophora SP-6.

    PubMed

    Emerson, D; Ghiorse, W C

    1993-12-01

    Isolated sheaths of Leptothrix discophora SP-6 (ATCC 51168) were tested for susceptibility to degradation by a variety of chemical denaturants and lytic enzymes and found to be resistant to many reagents and enzyme treatments. However, disulfide bond-reducing agents such as dithiothreitol (DTT), beta-mercaptoethanol, sodium cyanide, and sodium sulfite degraded the sheath, especially at elevated pH (pH 9) and temperature (50 degrees C). DTT and beta-mercaptoethanol caused more rapid degradation of the sheath than cyanide or sulfite. Treatment of the sheath with 1 N NaOH resulted in rapid breakdown, while treatment with 1 N HCl resulted in slow but significant hydrolysis. Transmission electron microscopy showed that the 6.5-nm fibrils previously shown to be an integral structural element of the sheath fabric (D. Emerson and W. C. Ghiorse, J. Bacteriol. 175:7808-7818, 1993) were progressively dissociated into random masses during DTT-induced degradation. Quantitation of disulfide bonds with DTT showed that the sheaths contained approximately 2.2 mumol of disulfides per mg of sheath protein. Reaction with 5,5'-dithio-bis-(2-nitrobenzoic acid) showed that sheaths also contained approximately 0.8 mumol of free sulfhydryls per mg of protein. A sulfhydryl-specific fluorescent probe (fluorescein 5-maleimide) showed that the free sulfhydryls in sheathed cell filaments were evenly distributed throughout the sheath. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis autoradiography of [14C]iodoacetamide-labeled sheaths and DTT-dissociated sheath fibril suspensions showed that the majority of 14C-labeled sulfhydryls in the sheaths did not enter the gel. However, low-molecular-mass silver-staining bands (14 to 45 kDa) did appear in the gels after iodoacetic acid or iodoacetamide alkylation of the dissociated fibrils. These bands did not stain with Coomassie blue. Their migration in gels was slightly affected by digestion with pronase. The fibrils contained 20 to 25

  4. Sheath liquid effects in capillary high-performance liquid chromatography-electrospray mass spectrometry of oligonucleotides.

    PubMed

    Huber, C G; Krajete, A

    2000-02-18

    Fused-silica capillary columns of 200 microm inner diameter were packed with micropellicular, octadecylated, 2.3 microm poly(styrene-divinylbenzene) particles and applied to the separation of oligonucleotides by ion-pair reversed-phase high-performance liquid chromatography. Oligonucleotides were eluted at 50 degrees C with gradients of 3-13% acetonitrile in 50 mM triethylammonium bicarbonate. Addition of sheath liquid to the column effluent allowed the detection of oligonucleotides by electrospray ionization mass spectrometry using full-scan data acquisition with a detectability comparable to that obtained with UV detection. The signal-to-noise ratios with different sheath liquids increased in the order isopropanolsheath liquid was found to influence the charge state distribution of oligonucleotides longer than 20 nucleotide units whereas no significant effect was observed with shorter oligonucleotides. Organic acids and bases in the sheath liquid generally deteriorated the signal-to-noise ratios in the chromatograms and mass spectra mainly because of increased background noise. Only a few charge states were observed in the mass spectra of oligonucleotides because of charge state reduction due to the presence of carbonic acid in the eluent. With triethylammonium hydrogencarbonate as chromatographic eluent and acetonitrile as sheath liquid, very few cation adducts of oligonucleotides were observed in the mass spectra. However, the presence of small amounts of monopotassium adducts enabled the calculation of the charge state of multiply charged ions. With acetonitrile as sheath liquid, 710 amol of a 16-mer oligonucleotide were detected using selected ion monitoring data acquisition with a signal-to-noise ratio of 3:1. Finally, capillary ion-pair reversed-phase high-performance liquid chromatography-electrospray ionization mass spectrometry was

  5. Laser-induced fluorescence measurement of the dynamics of a pulsed planar sheath

    NASA Astrophysics Data System (ADS)

    Goeckner, M. J.; Malik, Shamim M.; Conrad, J. R.; Breun, R. A.

    1994-04-01

    Using laser-induced fluorescence (LIF) the ion density near the edge of an expanding plasma sheath has been measured. These measurements utilized a transition of N+2 [the P12 component of the X 2Σ+g(ν=0)→B 2Σ+u(ν=0) band] in a N2 plasma. The strength of the laser-induced fluorescence was used as a measure of the temporally and spatially varying ion density. The expanding sheath was produced by applying a -5 kV pulse to a polished planar electrode in the plasma source ion implantation device [J. R. Conrad et al., J. Vac. Sci. Technol. A 8, 3146 (1990)]. The laser beam was aligned normal to the surface and was reflected off the center of the electrode. The LIF diagnostic used here is nonperturbing whereas previous researchers have used Langmuir probes, which perturb the plasma, to make their measurements. As such, the data reported here represent a benchmark measurement of pulsed sheaths and allow a better comparison between experimental measurements and theoretical predictions. It has been found that the sheath edge moves approximately 16 times faster than the ion-acoustic velocity during the early part of the pulse, t<1 μs, and then slows to approximately the ion-acoustic velocity after 6 μs. In addition to the LIF measurements, a biased probe was used far from the cathode to determine the sheath edge location. Good agreement is found when the LIF and probe data are compared. The LIF data also are compared to the predictions of a simulation that is based on a time-varying two-fluid model of the sheath [G. A. Emmert and M. A. Henry, J. Appl. Phys. 71, 113 (1992)]. While the predictions of the model show moderate agreement with the data, substantial discrepancies are observed. These discrepancies are attributed to a number of physical phenomena that are not included in the present model.

  6. Application of Spray Foam Insulation Under Plywood and Oriented Strand Board Roof Sheathing

    SciTech Connect

    Grin, A.; Smegal, J.; Lstiburek, J.

    2013-10-01

    Unvented roof strategies with open cell and closed cell spray polyurethane foam insulation sprayed to the underside of roof sheathing have been used since the mid-1990's to provide durable and efficient building enclosures. However, there have been isolated moisture related incidents reported anecdotally that raise potential concerns about the overall hygrothermal performance of these systems. The incidents related to rainwater leakage and condensation concerns. Condensation concerns have been extensively studied by others and are not further discussed in this report. This project involved hygrothermal modeling of a range of rainwater leakage and field evaluations of in-service residential roofs using spray foam insulation. All of the roof assemblies modeled exhibited drying capacity to handle minor rainwater leakage. All field evaluation locations of in-service residential roofs had moisture contents well within the safe range for wood-based sheathing. Explorations of eleven in-service roof systems were completed. The exploration involved taking a sample of spray foam from the underside of the roof sheathing, exposing the sheathing, then taking a moisture content reading. All locations had moisture contents well within the safe range for wood-based sheathing. One full-roof failure was reviewed, as an industry partner was involved with replacing structurally failed roof sheathing. In this case the manufacturer's investigation report concluded that the spray foam was installed on wet OSB based on the observation that the spray foam did not adhere well to the substrate and the pore structure of the closed cell spray foam at the ccSPF/OSB interface was indicative of a wet substrate.

  7. The coexistence of peripheral nerve sheath tumors and vitiligo: more than coincidence?

    PubMed

    Elsherif, Mohamed A; Spinner, Robert J; Miest, Rachel Y

    2016-01-01

    Neurocristopathies arise from abnormal migration, differentiation, or proliferation of neural crest derivatives, leading to diverse clinical and pathological features. They are classified into dysgenetic or neoplastic, and can affect single or multiple sites (simple versus complex). Examples include congenital melanocytic nevi, neuroblastoma, Hirshsprung's disease, Waardenburg's syndrome, neurofibromatosis (NF) 1 and multiple endocrine neoplasia (MEN) 2A and 2B. We report two cases of peripheral nerve sheath tumors associated with vitiligo and discuss the possible implicated embryologic, genetic and molecular mechanisms. To our knowledge, we also report the first case of de novo malignant peripheral nerve sheath tumor (MPNST) associated with vitiligo. PMID:26607956

  8. Parameters of a collisional radio-frequency sheath and dust characteristics resulting from the microparticle levitation

    SciTech Connect

    Yaroshenko, V. V.; Antonova, T.; Thomas, H. M.; Morfill, G. E.

    2009-10-15

    The screening length, the time-average electric field, and the particle charge as well as the local vertical gradients of these quantities are determined experimentally within a sheath of a capacitively coupled rf, 13.56 MHz, discharge at enhanced argon gas pressures of 30, 55, and 100 Pa. The parameters are derived directly from comparative measurements of levitation positions of the particles of different sizes and variations in the levitation heights caused by formation of new dust layers. The electrostatic effect of the horizontally extended dust layers on the sheath electric field is investigated.

  9. Child-Langmuir law applicability for a cathode sheath description of glow discharge in hydrogen

    NASA Astrophysics Data System (ADS)

    Lisovskiy, V. A.; Artushenko, K. P.; Yegorenkov, V. D.

    2016-08-01

    The present paper reveals that the Child-Langmuir law version with the constant ion mobility has to be applied for the cathode sheath description of the glow discharge in hydrogen. Using the analytical model we demonstrate that even in a high electric field the constant mobility law version rather than that for the constant ion mean free path has to hold in the case of impeded charge exchange and the dominant effect of polarization forces on the ion motion through the cathode sheath.

  10. General Cause of Sheath Instability Identified for Low Collisionality Plasma in Devices with Secondary Electron Emission

    SciTech Connect

    M.C. Campanell, A. Khrabrov and I Kaganovich

    2012-05-11

    A condition for sheath instability due to secondary electron emission (SEE) is derived for low collisionality plasmas. When the SEE coefficient of the electrons bordering the depleted loss cone in energy space exceeds unity, the sheath potential is unstable to a negative perturbation. This result explains three different instability phenomena observed in Hall thruster simulations including a newly found state with spontaneous ~20MHz oscillations. When instabilities occur, the SEE propagating between the walls becomes the dominant contribution to the particle flux, energy loss and axial transport.

  11. Child–Langmuir law applicability for a cathode sheath description of glow discharge in hydrogen

    NASA Astrophysics Data System (ADS)

    Lisovskiy, V. A.; Artushenko, K. P.; Yegorenkov, V. D.

    2016-08-01

    The present paper reveals that the Child-Langmuir law version with the constant ion mobility has to be applied for the cathode sheath description of the glow discharge in hydrogen. Using the analytical model we demonstrate that even in a high electric field the constant mobility law version rather than that for the constant ion mean free path has to hold in the case of impeded charge exchange and the dominant effect of polarization forces on the ion motion through the cathode sheath.

  12. Sheath effects on current collection by particle detectors with narrow acceptance angles

    NASA Technical Reports Server (NTRS)

    Singh, N.; Baugher, C. R.

    1981-01-01

    Restriction of the aperture acceptance angle of an ion or electron trap on an attracting spacecraft significantly alters the volt-ampere characteristics of the instrument in a low Mach number plasma. It is shown when the angular acceptance of the aperture is restricted the current to the collector tends to be independent of the Debye length. Expressions for the RPA characteristics for both a thin sheath and a thick sheath are derived; and it is shown that as the aperture is narrowed the curves tend toward equivalence.

  13. The coexistence of peripheral nerve sheath tumors and vitiligo: more than coincidence?

    PubMed

    Elsherif, Mohamed A; Spinner, Robert J; Miest, Rachel Y

    2016-01-01

    Neurocristopathies arise from abnormal migration, differentiation, or proliferation of neural crest derivatives, leading to diverse clinical and pathological features. They are classified into dysgenetic or neoplastic, and can affect single or multiple sites (simple versus complex). Examples include congenital melanocytic nevi, neuroblastoma, Hirshsprung's disease, Waardenburg's syndrome, neurofibromatosis (NF) 1 and multiple endocrine neoplasia (MEN) 2A and 2B. We report two cases of peripheral nerve sheath tumors associated with vitiligo and discuss the possible implicated embryologic, genetic and molecular mechanisms. To our knowledge, we also report the first case of de novo malignant peripheral nerve sheath tumor (MPNST) associated with vitiligo.

  14. Calculation of two-dimensional plasma sheath with application to radial dust oscillations

    SciTech Connect

    Sheridan, T.E.

    2005-07-15

    Dust particles are often confined radially in a plasma potential well above a cylindrical depression in an otherwise flat electrode. The structure of the two-dimensional, time-independent sheath is computed for this geometry using cold, collisionless ions and Boltzmann electrons. A depression with a radius of 16 Debye lengths and a depth of 2 Debye lengths is modeled for negative electrode biases from 6 to 32 times the electron temperature. The normalized radial oscillation frequency for a dust particle in the well is computed from the sheath potential structure. The model results agree qualitatively with the experimental measurements.

  15. Modelling of Charged Particle Dynamics in the Sheath and Plasma-facing Surface Sputtering

    NASA Astrophysics Data System (ADS)

    Borodkina, I. E.; Tsvetkov, I. V.

    In this work a useful analytical approximation for the electric potential profile in the presence of an oblique magnetic field is suggested. It describes the potential profile dependence on the magnitude and angle of a magnetic field and plasma parameters in the Debye sheath and the magnetic pre-sheath. It is in good agreement with the Chodura and Stangeby solutions and respective PIC simulations performed with the SPICE2 code. The influence of the magnetic field inclination angle on the angle and energy distributions of ions which reach the wall, and thus on the effective sputtering, is analyzed for various first wall materials.

  16. From electron depletion to quasi-neutrality: the sheath-bulk transition in RF modulated discharges

    NASA Astrophysics Data System (ADS)

    Brinkmann, Ralf Peter

    2009-10-01

    The boundary sheaths of all plasmas are characterized by a gradual transition from unipolarity (electron depletion, ne Lt ni) to ambipolarity (quasi-neutrality, ne ≈ ni). Capacitively driven sheaths exhibit a transition which is expanded by the RF modulation and smoothed by thermal effects, i.e. by the finiteness of the electron temperature Te and the Debye length \\lambda_D = \\sqrt{\\epsilon_0 T_e/e^2 n_e} . Sheath models which neglect thermal effects ('step models') are restricted to strongly modulated high voltage sheaths with VRF Gt Te/e and fail when this condition is not met. This work presents an improved analysis of the sheath-bulk transition which takes both modulation and thermal effects into account. Based on a previously found asymptotic solution of the Boltzmann-Poisson equation (Brinkmann 2007 J. Appl. Phys. 102 093393), approximate algebraic (i.e. closed) expressions for the phase-resolved electrical field E and electron density ne in RF sheaths are derived. Under the assumption that the modulation is periodic (not necessarily harmonic) with ωRF Gt ωpi, also the phase averages of the field \\bar E and the electron density {\\bar n}_e can be expressed in closed form. These results—together referred to as the advanced algebraic approximation (AAA)—make it possible to formulate efficient and accurate models for RF driven boundary sheaths for all ratios of VRF to Te/e. As an example, a harmonically RF modulated, collision-dominated single species sheath is studied. The outcome is compared both with the numerically constructed exact solution and with the well-known step model approach of Lieberman (1989 IEEE Trans. Plasma Sci. 17 338). It is found that the AAA can reproduce the exact numerical solution within a few per cent for all ratios of VRF to Te/e. The step model, in contrast, exhibits strong deviations even for large eVRF/Te and fails completely in the case of weak modulation.

  17. Numerical investigation of fast-wave propagation and radio-frequency sheath interaction with a shaped tokamak wall

    SciTech Connect

    Kohno, H.; Myra, J. R.; D'Ippolito, D. A.

    2015-07-15

    Interactions between propagating fast waves and radio-frequency (RF) sheaths in the ion cyclotron range of frequencies are numerically investigated based on a cold fluid plasma model coupled with a sheath boundary condition. In this two-dimensional study, the capability of the finite element code rfSOL, which was developed in previous numerical work, is extended to analyze self-consistent RF sheath-plasma interaction problems in a tokamak with a non-circular cross-section. It is found that a large sheath voltage is generated near the edges of the limiter-shaped deformation as a result of the conversion from fast to slow waves on the sheaths. The sheath voltage associated with this conversion is particularly significant in the localized region where the contact angle between the magnetic field line and the conducting wall varies rapidly along the curved sheath surface, which is consistent with the results in previous one-dimensional theoretical work. The dependences of the RF sheaths on various parameters in plasma such as the toroidal wavenumber, edge plasma density, and the degree of the RF wave absorption in the core region are also examined in detail.

  18. Influence of ion-neutral collision parameters on dynamic structure of magnetized sheath during plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Khoram, Mansour; Ghomi, Hamid

    2016-03-01

    A cold magnetized plasma sheath is considered to examine the gas pressure effect on the sheath dynamics. A fluid model is used to describe the plasma sheath dynamic. The governing fluid equations in the plasma are solved from plasma center to the target using the finite difference method and some convenient initial and boundary conditions at the plasma center and target. It is found that, the ion-neutral collision has significant effect on the dynamic characteristics of the high-voltage sheath in the plasma immersion ion implantation (PIII). It means that, the temporal profile of the ion dose on the target and sheath width are decreased by increasing the gas pressure. Also, the gas pressure substantially diminishes the temporal psychograph of ion incident angle on the target.

  19. Numerical analysis of radio-frequency sheath-plasma interactions in the ion cyclotron range of frequencies

    SciTech Connect

    Kohno, H.; Myra, J. R.; D'Ippolito, D. A.

    2012-01-15

    A new finite element numerical scheme for analyzing self-consistent radio-frequency (RF) sheath-plasma interaction problems in the ion cyclotron range of frequencies is applied to various problems represented by simplified models for the tokamak scrape-off layer. The present code incorporates a modified boundary condition, which is called a sheath boundary condition, that couples the radio-frequency waves and sheaths at the material boundaries by treating the sheath as a thin vacuum layer. A series of numerical analyses in one- and two-dimensional domains show several important physical properties, such as the existence of multiple roots, hysteresis effects, presence and characteristics of the sheath-plasma waves, and the phase shift of a reflected slow wave, some of which are newly identified by introducing a spatially varying plasma density and background magnetic field.

  20. Fine structure of modal focusing effect in a three dimensional plasma-sheath-lens formed by disk electrodes

    NASA Astrophysics Data System (ADS)

    Stamate, Eugen; Yamaguchi, Masahito

    2015-08-01

    Modal and discrete focusing effects associated with three-dimensional plasma-sheath-lenses show promising potential for applications in ion beam extraction, mass spectrometry, plasma diagnostics and for basic studies of plasma sheath. The ion focusing properties can be adjusted by controlling the geometrical structure of the plasma-sheath-lens and plasma parameters. The positive and negative ion kinetics within the plasma-sheath-lens are investigated both experimentally and theoretically and a modal focusing ring is identified on the surface of disk electrodes. The focusing ring is very sensitive to the sheath thickness and can be used to monitor very small changes in plasma parameters. Three dimensional simulations are found to be in very good agreement with experiments.

  1. Fine structure of modal focusing effect in a three dimensional plasma-sheath-lens formed by disk electrodes

    SciTech Connect

    Stamate, Eugen; Yamaguchi, Masahito

    2015-08-31

    Modal and discrete focusing effects associated with three-dimensional plasma-sheath-lenses show promising potential for applications in ion beam extraction, mass spectrometry, plasma diagnostics and for basic studies of plasma sheath. The ion focusing properties can be adjusted by controlling the geometrical structure of the plasma-sheath-lens and plasma parameters. The positive and negative ion kinetics within the plasma-sheath-lens are investigated both experimentally and theoretically and a modal focusing ring is identified on the surface of disk electrodes. The focusing ring is very sensitive to the sheath thickness and can be used to monitor very small changes in plasma parameters. Three dimensional simulations are found to be in very good agreement with experiments.

  2. Multistate evaluation of Brassica cover crop, biocontrol agent, and fungicide for integrated management of sheath blight

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sheath blight, caused by Rhizoctonia solani, is one of the most important diseases limiting rice production in the southern rice-producing states. The fungus survives between crops as sclerotia and mycelia in infected plant debris and serves as the primary inoculum. Infection starts when sclerotia a...

  3. Influence of sheath solvents on the quality of ethyl cellulose nanofibers in a coaxial electrospinning process.

    PubMed

    Yu, Deng-Guang; Li, Xiao-Yan; Chian, Wei; Li, Ying; Wang, Xia

    2014-01-01

    The influence of different types of solvents as sheath fluids on the quality of electrospun ethyl cellulose (EC) nanofibers is investigated in this paper by a modified coaxial process. With 24 w/v % EC in ethanol as electrospinning core fluid and pure solvents including methanol, ethanol and N,N-dimethyl formamide (DMF) as sheath fluids, EC nanofibers were generated by the modified processes. Field emission scanning electron microscope observations demonstrate that the modified process is effective in improving the nanofibers' quality in terms of nanofibers' diameters, distributions and structural uniformity. The key of the modified coaxial process is the reasonable selection of the sheath solvents that is suitable for the drawing process of core EC fluid during the electrpospinning. The EC nanofibers' diameters (D, nm) could be manipulated through the reasonable selection of the type of the sheath solvents based on their boiling point (T, °C) D = 841-3.71T (R=0.9753). This paper provides useful methods for the implementation of the modified coaxial process controllably to obtain polymer nanofibers with high quality.

  4. Screening and sheath formation in a nonequilibrium mixed Cairns-Tsallis electron distribution

    SciTech Connect

    Bouzit, Omar; Gougam, Leila Ait; Tribeche, Mouloud

    2015-05-15

    The effects of electron nonextensivity for a given nonthermality state, on Debye shielding and electrostatic sheath formation are examined. A physically meaningful Cairns-Tsallis distribution is outlined and a generalized expression for the Debye screening length λ{sub D}{sup q,α} is obtained. It is shown that an increase of the entropic index q causes λ{sub D}{sup q,α} to decrease whatever the amount of plasma nonthermality α. In addition, smaller pertinent values of q along with relatively higher values of α provide larger values of λ{sub D}{sup q,α}. The shielded electrostatic potential falls off as a function of distance more slowly as α increases, a result somewhat analogous to the dynamical shielding decrease (albeit in a different context) of a free charge as it begins to move. Moreover, smaller pertinent values of q along with relatively higher values of α are found to involve higher ion drift speed v{sub i0} for proper sheath formation. As α increases, the sheath electrostatic potential-gradient dΨ{sub s}/dξ becomes abruptly steep slowing down the energetic electrons leakage to the wall. Moreover, the sheath thickness broadens as the electron nonthermality strengthens.

  5. An analytic expression for the sheath criterion in magnetized plasmas with multi-charged ion species

    SciTech Connect

    Hatami, M. M.

    2015-04-15

    The generalized Bohm criterion in magnetized multi-component plasmas consisting of multi-charged positive and negative ion species and electrons is analytically investigated by using the hydrodynamic model. It is assumed that the electrons and negative ion density distributions are the Boltzmann distribution with different temperatures and the positive ions enter into the sheath region obliquely. Our results show that the positive and negative ion temperatures, the orientation of the applied magnetic field and the charge number of positive and negative ions strongly affect the Bohm criterion in these multi-component plasmas. To determine the validity of our derived generalized Bohm criterion, it reduced to some familiar physical condition and it is shown that monotonically reduction of the positive ion density distribution leading to the sheath formation occurs only when entrance velocity of ion into the sheath satisfies the obtained Bohm criterion. Also, as a practical application of the obtained Bohm criterion, effects of the ionic temperature and concentration as well as magnetic field on the behavior of the charged particle density distributions and so the sheath thickness of a magnetized plasma consisting of electrons and singly charged positive and negative ion species are studied numerically.

  6. Analysis of rice PDR-like ABC transporter genes in sheath blight resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sheath blight caused by Rhizoctonia solani is one of the most damaging diseases of rice worldwide. To understand the molecular mechanism of resistance, we identified 450 differentially expressed genes in a resistant rice cultivar Jasmine 85 after R. solani infection with a combination of DNA microar...

  7. Sensitivity to a Phytotoxin from Rhizoctonia solani Correlates with Sheath Blight Susceptibility in Rice.

    PubMed

    Brooks, Steven A

    2007-10-01

    ABSTRACT Sheath blight is one of the most important and intractable diseases of rice (Oryza sativa) where limited control has been achieved using traditional approaches. Quantitative inheritance, extraneous traits, and environmental factors confound genetic analysis of host resistance. A method was developed to isolate and utilize a phytotoxin from Rhizoctonia solani to investigate the genetics of sheath blight susceptibility. Infiltration of the toxin preparation into plant leaves induced necrosis in rice, maize, and tomato. Using 17 rice cultivars known to vary in sheath blight resistance, genotypes were identified that were sensitive (tox-S) and insensitive (tox-I) to the toxin, and a correlation (r = 0.66) between toxin sensitivity and disease susceptibility was observed. Given the broad host range of R. solani, genotypes of host species may be both tox-S and tox-I. A total of 154 F(2) progeny from a cross between Cypress (tox-S) and Jasmine 85 (tox-I) segregated in a 9:7 ratio for tox-S/tox-I, indicating an epistatic interaction between two genes controls sensitivity to the toxin in rice. This work provides the means to genetically map toxin sensitivity genes and eliminate susceptible genotypes when developing sheath blight-resistant rice cultivars.

  8. Effect of optic nerve sheath fenestration for idiopathic intracranial hypertension on retinal nerve fiber layer thickness.

    PubMed

    Starks, Victoria; Gilliland, Grant; Vrcek, Ivan; Gilliland, Connor

    2016-01-01

    The objective of the study was to evaluate whether optic nerve sheath fenestration in patients with idiopathic intracranial hypertension was associated with improvement in visual field pattern deviation and optical coherence tomography retinal nerve fiber layer thickness.The records of 13 eyes of 11 patients who underwent optic nerve sheath fenestration were reviewed. The subjects were patients of a clinical practice in Dallas, Texas. Charts were reviewed for pre- and postoperative visual field pattern deviation (PD) and retinal nerve fiber layer thickness (RNFL).PD and RNFL significantly improved after surgery. Average PD preoperatively was 8.51 DB and postoperatively was 4.80 DB (p = 0.0002). Average RNFL preoperatively was 113.63 and postoperatively was 102.70 (p = 0.01). The preoperative PD and RNFL did not correlate strongly.Our results demonstrate that PD and RNFL are improved after optic nerve sheath fenestration. The pre- and postoperative RNFL values were compared to the average RNFL value of healthy optic nerves obtained from the literature. Post-ONSF RNFL values were significantly closer to the normal value than preoperative. RNFL is an objective parameter for monitoring the optic nerve after optic nerve sheath fenestration. This study adds to the evidence that OCT RNFL may be an effective monitoring tool for patients with IIH and that it continues to be a useful parameter after ONSF.

  9. Genetic and genomic dissection of resistance genes to the rice sheath blight pathogen

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rice sheath blight disease caused by the anastomosis group AG1-IA of the fungal pathogen Rhizoctonia solani is one of the most serious rice diseases in the southern US and the world. The use of fungicides is a popular but costly method to control this disease worldwide. Genetic analysis of host re...

  10. Characterization of tail sheath protein of giant bacteriophage phiKZ Pseudomonas aeruginosa

    SciTech Connect

    Kurochkina, Lidia P.; Sachkova, Maria Yu.; Sykilinda, Nina N.; Mesyanzhinov, Vadim V.

    2009-12-20

    The tail sheath protein of giant bacteriophage phiKZ Pseudomonas aeruginosa encoded by gene 29 was identified and its expression system was developed. Localization of the protein on the virion was confirmed by immunoelectron microscopy. Properties of gene product (gp) 29 were studied by electron microscopy, immunoblotting and limited trypsinolysis. Recombinant gp29 assembles into the regular tubular structures (polysheaths) of variable length. Trypsin digestion of gp29 within polysheaths or extended sheath of virion results in specific cleavage of the peptide bond between Arg135 and Asp136. However, this cleavage does not affect polymeric structure of polysheaths, sheaths and viral infectivity. Digestion by trypsin of the C-truncated gp29 mutant, lacking the ability to self-assemble, results in formation of a stable protease-resistant fragment. Although there is no sequence homology of phiKZ proteins to proteins of other bacteriophages, some characteristic biochemical properties of gp29 revealed similarities to the tail sheath protein of bacteriophage T4.

  11. RiceCAP: Progress in identifying QTL for sheath blight resistance and milling yield

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The RiceCAP project was initiated to utilize genomics to address two recalcitrant breeding traits that are economically important to the US rice industry. Sheath blight disease resistance (SB) and rice milling yield (MY) are both complexly inherited traits, sensitive to environmental fluctuations, a...

  12. 3D visualization of sheath folds in Ancient Roman marble wall coverings from Ephesos, Turkey

    NASA Astrophysics Data System (ADS)

    Wex, Sebastian; Passchier, Cees W.; de Kemp, Eric A.; İlhan, Sinan

    2014-10-01

    Archaeological excavations and restoration of a palatial Roman housing complex in Ephesos, Turkey yielded 40 wall-decorating plates of folded mylonitic marble (Cipollino verde), derived from the internal Hellenides near Karystos, Greece. Cipollino verde was commonly used for decoration purposes in Roman buildings. The plates were serial-sectioned from a single quarried block of 1,25 m3 and provided a research opportunity for detailed reconstruction of the 3D geometry of meterscale folds in mylonitized marble. A GOCAD model is used to visualize the internal fold structures of the marble, comprising curtain folds and multilayered sheath folds. The sheath folds are unusual in that they have their intermediate axis normal to the parent layering. This agrees with regional tectonic studies, which suggest that Cipollino verde structures formed by local constrictional non-coaxial flow. Sheath fold cross-section geometry, exposed on the surface of a plate or outcrop, is found to be independent of the intersection angle of the fold structure with the studied plane. Consequently, a single surface cannot be used as an indicator of the three-dimensional geometry of transected sheath folds.

  13. Kinetic simulation of the sheath dynamics in the intermediate radio frequency regime

    NASA Astrophysics Data System (ADS)

    Shihab, M.; Elgendy, A. T.; Korolov, I.; Derzsi, A.; Schulze, J.; Eremin, D.; Mussenbrock, T.; Donkó, Z.; Brinkmann, R. P.

    2013-10-01

    The dynamics of temporally modulated plasma boundary sheaths is studied in the intermediate radio frequency regime where the applied radio frequency and the ion plasma frequency (or the reciprocal of the ion transit time) are comparable. Two fully kinetic simulation algorithms are employed and their results are compared. The first is a realization of the well-known particle-in-cell technique with Monte Carlo collisions and simulates the entire discharge, a planar radio frequency capacitively coupled plasma with an additional ionization source. The second code is based on the recently published scheme Ensemble-in-Spacetime (EST); it resolves only the sheath and requires the time-resolved voltage across and the ion flux into the sheath as input. Ion inertia causes a temporal asymmetry (hysteresis) of the charge-voltage relation; other ion transit time effects are also found. The two algorithms are in good agreement, both with respect to the spatial and temporal dynamics of the sheath and with respect to the ion energy distributions at the electrodes. It is concluded that the EST scheme may serve as an efficient post-processor for fluid or global simulations and for measurements: it can rapidly and accurately calculate ion distribution functions even when no genuine kinetic information is available.

  14. Fast, Kinetically self-consistent simulation of RF modulated plasma boundary sheaths

    NASA Astrophysics Data System (ADS)

    Shihab, Mohammed; Brinkmann, Ralf Peter

    2012-10-01

    A mathematical model is presented which enables the efficent, kinetically self-consistent simulation of RF modulated plasma boundary sheaths in all technically relevant discharge regimes. The model consists of a set of kinetic equations for the ions, Boltzmann's relation for the electrons and Poisson's equation for the electrical field. Boundary conditions specify the ion flux at a point deep in the bulk and a periodically modulated sheath voltage or sheath charge. The equations are solved in a statistical sense. However, it is not the well-known particle-in-cell (PIC) scheme that is employed, but an alternative iterative algorithm termed ensemble-in-spacetime (EST). Three modules are called in a sequence: a Monte Carlo module, a harmonic analysis module, and a field module. The iteration is started with the potential values of a self-consistent fluid model and terminates when the updates become sufficiently small, i.e. when self-consistency is achieved. A drastic reduction of the computational effort compared with PIC calculations is achieved. As a first application of the new model, the influence of ion inertia on the dynamics of a collisionless sheath is studied and a comparison of the simulated ion energy distribution with published analytical solutions is performed.

  15. A smart core-sheath nanofiber that captures and releases red blood cells from the blood.

    PubMed

    Shi, Q; Hou, J; Zhao, C; Xin, Z; Jin, J; Li, C; Wong, S-C; Yin, J

    2016-01-28

    A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.

  16. Evaluation of the USDA Rice Core Collection for sheath blight disease using micro-chamber

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The USDA rice core collection, including 1,794 accessions from 114 countries, was developed using a stratified random sampling method to represent the entire NSGC collection including over 18,000 accessions. Sheath blight (Rhizoctonia solani) is one of the most important and widely distributed disea...

  17. Searching for Germplasm Resistant to Sheath Blight from the USDA Rice Core Collection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sheath blight, caused by the fungal pathogen Rhizoctonia solani, is one of the most important and widely distributed diseases capable of infesting numerous crops including rice. Resistant germplasm with wide variation is essential for controlling this disease via breeding efforts, and genetic backgr...

  18. Pathology in practice: Peripheral nerve sheath tumor in a Shubunkin goldfish

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Peripheral nerve sheath tumors (PNSTs) have been detected in many fish species, including goldfish, several species of snapper, coho salmon, the bicolor damselfish, and rainbow smelt. They originate from neural crest cells and generally occur along the subcutaneous nerves. A viral etiology has bee...

  19. Self-powered energy fiber: energy conversion in the sheath and storage in the core.

    PubMed

    Yang, Zhibin; Deng, Jue; Sun, Hao; Ren, Jing; Pan, Shaowu; Peng, Huisheng

    2014-11-01

    A high-performance, self-powered, elastic energy fiber is developed that consists of an energy conversion sheath and an energy storage core. The coaxial structure and the aligned nanostructures at the electrode interface enable a high total energy-conversion and energy-storage performance that is maintained under bending and after stretching.

  20. Development of a Sheathed Miniature Aerothermal Reentry Thermocouple for Thermal Protection System Materials

    NASA Technical Reports Server (NTRS)

    Martinez, Edward R.; Weber, Carissa Tudryn; Oishi, Tomo; Santos, Jose; Mach, Joseph

    2011-01-01

    The Sheathed Miniature Aerothermal Reentry Thermocouple is a micro-miniature thermocouple for high temperature measurement in extreme environments. It is available for use in Thermal Protection System materials for ground testing and flight. This paper discusses the heritage, and design of the instrument. Experimental and analytical methods used to verify its performance and limitations are described.

  1. TssA forms a gp6-like ring attached to the type VI secretion sheath.

    PubMed

    Planamente, Sara; Salih, Osman; Manoli, Eleni; Albesa-Jové, David; Freemont, Paul S; Filloux, Alain

    2016-08-01

    The type VI secretion system (T6SS) is a supra-molecular bacterial complex that resembles phage tails. It is a killing machine which fires toxins into target cells upon contraction of its TssBC sheath. Here, we show that TssA1 is a T6SS component forming dodecameric ring structures whose dimensions match those of the TssBC sheath and which can accommodate the inner Hcp tube. The TssA1 ring complex binds the T6SS sheath and impacts its behaviour in vivo In the phage, the first disc of the gp18 sheath sits on a baseplate wherein gp6 is a dodecameric ring. We found remarkable sequence and structural similarities between TssA1 and gp6 C-termini, and propose that TssA1 could be a baseplate component of the T6SS Furthermore, we identified similarities between TssK1 and gp8, the former interacting with TssA1 while the latter is found in the outer radius of the gp6 ring. These observations, combined with similarities between TssF and gp6N-terminus or TssG and gp53, lead us to propose a comparative model between the phage baseplate and the T6SS. PMID:27288401

  2. The Geo-Effectiveness of CME-Driven Shocks and Sheaths

    NASA Astrophysics Data System (ADS)

    Lugaz, Noé; Al-haddad, Nada; Schwadron, Nathan; Riley, Pete; Farrugia, Charles; Winslow, Reka

    2016-07-01

    Past studies have found that ˜30% of intense geomagnetic storms and ˜20% of moderate geomagnetic storms are caused by forward fast magnetosonic shocks and the sheath plasma and magnetic field behind these shocks, making shocks the second most important cause of geomagnetic storms after magnetic ejecta. Since only about 20% of fast-mode shocks are followed by a moderate geomagnetic storm, it is important to understand which shock and upstream properties are most effective in creating optimal conditions for the development of geomagnetic storms. To do so, we identify all fast-mode forwards shocks (˜100), for which the sheath region resulted in a moderate or intense geomagnetic storm during solar cycles 23 and 24 (1997 - 2015). We find that about half such shocks are shocks propagating into a preceding CME or shocks propagating into the sheath region of a preceding shock. Overall, only a small fraction of shocks propagating through normal solar wind are geo-effective (less than 15%), whereas the majority of shocks propagating through a previous CME are geo-effective. We further discuss the conditions which can result in the formation of southward Bz in the sheath region behind a shock.

  3. The ion polytropic coefficient in a collisionless sheath containing hot ions

    NASA Astrophysics Data System (ADS)

    Lin, Binbin; Xiang, Nong; Ou, Jing

    2016-08-01

    The fluid approach has been widely used to study plasma sheath dynamics. For a sheath containing hot ions whose temperature is greater than the electron's, how to truncate the fluid hierarchy chain equations while retaining to the fullest extent of the kinetic effects is always a difficult problem. In this paper, a one-dimensional, collisionless sheath containing hot ions is studied via particle-in-cell simulations. By analyzing the ion energy equation and taking the kinetic effects into account, we have shown that the ion polytropic coefficient in the vicinity of the sheath edge is approximately constant so that the state equation with the modified polytropic coefficient can be used to close the hierarchy chain of the ion fluid equations. The value of the polytropic coefficient strongly depends on the hot ion temperature and its concentration in the plasma. The semi-analytical model is given to interpret the simulation results. As an application, the kinetic effects on the ion saturation current density in the probe theory are discussed.

  4. A computer-controlled apparatus for Seebeck inhomogeneity testing of sheathed thermocouples

    NASA Technical Reports Server (NTRS)

    Burkett, Cecil G., Jr.; Bauserman, Willard A., Jr.

    1993-01-01

    Mineral-insulated metal-sheathed (MIMS) thermocouple assemblies are used throughout industry and research facilities as a method of temperature measurement where requirements for either harsh environmental conditions exist, or where rigidity of the measurement probe is required. Seebeck inhomogeneity is the abnormal variation of the Seebeck coefficient from point to point in a material. It is not disclosed in conventional calibration. A standardized method of measuring thermoelectric inhomogeneity along the thermocouple probe length is not available. Therefore, calibration for sheathed probes normally does not include testing of probe inhomogeneity. The measurement accuracy would be severely impacted if significant inhomogeneity and a temperature gradient were present in the same region of the probe. A computer-controlled system for determining inhomogeneities was designed, fabricated, and tested. This system provides an accurate method for the identification of the location of inhomogeneity along the length of a sheathed thermocouple and for the quantification of the inhomogeneity. This paper will discuss the apparatus and procedure used to perform these tests and will present data showing tests performed on sheathed thermocouple probes.

  5. Numerical Model of the Plasma Sheath Generated by the Plasma Source Instrument Aboard the Polar Satellite

    NASA Technical Reports Server (NTRS)

    Singh, N.; Leung, W. C.; Moore, T. E.; Craven, P. D.

    2001-01-01

    The plasma sheath generated by the operation of the Plasma Source Instrument (PSI) aboard the Polar satellite is studied by using a three-dimensional particle-in-cell (PIC) code. When the satellite passes through the region of low-density plasma, the satellite charges to positive potentials as high as 40-50 V, owing to the photoelectron emission. In such a case, ambient core ions cannot accurately be measured or detected. The goal of the onboard PSI is to reduce the floating potential of the satellite to a sufficiently low value so that the ions in the polar wind become detectable. When the PSI is operated, ion-rich xenon plasma is ejected from the satellite, such that the floating potential of the satellite is reduced and is maintained at approximately 2 V. Accordingly, in our three-dimensional PIC simulation we considered that the potential of the satellite is 2 V as a fixed bias. Considering the relatively high density of the xenon plasma in the sheath (10-10(exp 3)/cc), the ambient plasma of low density (<1/cc) is neglected. In the simulations the electric fields and plasma dynamics are calculated self-consistently. We found that an 'apple'-shape positive potential sheath forms surrounding the satellite. In the region near the PSI emission a high positive potential hill develops. Near the Thermal Ion Dynamics Experiment detector away from the PSI, the potentials are sufficiently low for the ambient polar wind ions to reach it. In the simulations it takes only about a couple of tens of electron gyroperiods for the sheath to reach a quasi steady state. This time is approximately the time taken by the heavy Xe(+) ions to expand up to about one average Larmor radius of electrons from the satellite surface. After this time the expansion of the sheath in directions transverse to the ambient magnetic field slows down because the electrons are magnetized. Using the quasi steady sheath, we performed trajectory calculations to characterize the detector response to a

  6. A new technique for immediate endoscopic realignment of post-traumatic bulbar urethral rupture

    PubMed Central

    Han, Congxiang; Li, Jinyu; Lin, Xiacong; Yu, Zhongying; Zhu, Xianzhong; Xu, Weijie; Li, Wei

    2015-01-01

    Objectives: Urethral injury with partial or complete disruption of urethral integrity can lead to voiding problems and serious infections. We report a new management technique involving immediate endoscopic realignment with drainage via peel-away sheath for post-traumatic bulbar urethral rupture. Methods: Thirteen patients presenting with post-traumatic bulbar urethral rupture between July 2010 and May 2013 were treated. An 18F peel-away sheath was inserted into the anterior urethra, then a ureteroscope or nephroscope was inserted into the peel-away sheath with continuous normal saline infusion and drainage through the cavity between ureteroscope and sheath to maintain operative field clarity. A guide wire was negotiated across the disruption to the bladder and an 18F Foley catheter inserted for 2-4 weeks. Rupture severity was evaluated by urethroscopy during operation. Two patients had partial urethral rupture and 11 complete rupture. Before Foley catheter removal, pericatheter urethrography was performed to determine if urinary extravasation had occurred. Urethroscopy was performed after catheter removal. Follow-up uroflowmetry was conducted monthly for 1 year. Results: This technique was successful in all patients and none experienced urinary extravasation or required open surgery. Mean operation time was 4.9±1.6 min (3-8 min) and the mean Foley catheter indwelling time was 25.8±5.3 days. During follow-up (18.4±5.4 months, 12-26 months), 6 patients developed urethral strictures (8.7±10.5 weeks, 1-28 weeks post-treatment). Strictures were managed by internal urethrotomy (1 patient) or urethral sound dilation (5) without open urethroplasty. Conclusions: Immediate endoscopic realignment with drainage via peel-away sheath is a fast, effective, and safe technique for bulbar urethral rupture. PMID:26550310

  7. Sheath expansion and plasma dynamics in the presence of electrode evaporation: Application to a vacuum circuit breaker

    SciTech Connect

    Sarrailh, P.; Garrigues, L.; Hagelaar, G. J. M.; Boeuf, J. P.; Sandolache, G.; Rowe, S.

    2009-09-01

    During the postarc dielectric recovery phase in a vacuum circuit breaker, a cathode sheath forms and expels the plasma from the electrode gap. The success or failure of current breaking depends on how efficiently the plasma is expelled from the electrode gap. The sheath expansion in the postarc phase can be compared to sheath expansion in plasma immersion ion implantation except that collisions between charged particles and atoms generated by electrode evaporation may become important in a vacuum circuit breaker. In this paper, we show that electrode evaporation plays a significant role in the dynamics of the sheath expansion in this context not only because charged particle transport is no longer collisionless but also because the neutral flow due to evaporation and temperature gradients may push the plasma toward one of the electrodes. Using a hybrid model of the nonequilibrium postarc plasma and cathode sheath coupled with a direct simulation Monte Carlo method to describe collisions between heavy species, we present a parametric study of the sheath and plasma dynamics and of the time needed for the sheath to expel the plasma from the gap for different values of plasma density and electrode temperatures at the beginning of the postarc phase. This work constitutes a preliminary step toward understanding and quantifying the risk of current breaking failure of a vacuum arc.

  8. A model symbiosis reveals a role for sheathed-flagellum rotation in the release of immunogenic lipopolysaccharide

    PubMed Central

    Brennan, Caitlin A; Hunt, Jason R; Kremer, Natacha; Krasity, Benjamin C; Apicella, Michael A; McFall-Ngai, Margaret J; Ruby, Edward G

    2014-01-01

    Bacterial flagella mediate host–microbe interactions through tissue tropism during colonization, as well as by activating immune responses. The flagellar shaft of some bacteria, including several human pathogens, is encased in a membranous sheath of unknown function. While it has been hypothesized that the sheath may allow these bacteria to evade host responses to the immunogenic flagellin subunit, this unusual structural feature has remained an enigma. Here we demonstrate that the rotation of the sheathed flagellum in both the mutualist Vibrio fischeri and the pathogen Vibrio cholerae promotes release of a potent bacteria-derived immunogen, lipopolysaccharide, found in the flagellar sheath. We further present a new role for the flagellar sheath in triggering, rather than circumventing, host immune responses in the model squid-vibrio symbiosis. Such an observation not only has implications for the study of bacterial pathogens with sheathed flagella, but also raises important biophysical questions of sheathed-flagellum function. DOI: http://dx.doi.org/10.7554/eLife.01579.001 PMID:24596150

  9. Gene profiling in the dynamic regulation of the lifespan of the myelin sheath structure in the optic nerve of rats.

    PubMed

    Xie, Fang; Fu, Han; Zhang, Jiu-Cong; Chen, Xue-Feng; Wang, Xiao-Liang; Chen, Jun

    2014-07-01

    Aging of the nervous system leads to impairments in cognition and motor skills, and is a major risk factor for several neurological disorders. Recently, numerous nerve function deficits that appear with aging have been found to be a consequence of myelin abnormalities; however, the genetic mechanism of the age‑related alterations in the myelin sheath has not yet been fully elucidated. In the present study, the morphology of the myelin sheath in the optic nerve of rats was analyzed at 10 time‑points throughout life. Marked alterations in the myelin sheath were observed in aging and aged optic nerves, and these became progressively more severe with time. To determine the biological processes affected by aging in the myelin sheath, the age‑related profiling of the myelin sheath in rat optic nerves was established using microarray hybridization at 10 time‑points throughout life, between birth and senescence. From the results, 3,826 transcripts associated with the age‑related alterations in the myelin sheath of the optic nerve were identified. It was found that the biological processes most significantly altered by aging were lipid metabolism, the immune response and transmitter transport. This suggests that the downregulation of lipid synthesis genes and the upregulation of immune and neurotransmitter transport genes in aging may be the genetic basis for the age‑related alterations observed in the myelin sheath.

  10. Persistent spontaneous synovial drainage from digital flexor sheath in proliferative tenosynovitis: Two case reports and a review of the literature

    PubMed Central

    Chin, Brian; Cheung, Kevin; Farhangkhoee, Hana; Thoma, Achilleas

    2015-01-01

    Proliferative flexor tenosynovitis of the hand is an inflammatory process involving the synovial sheaths surrounding the tendons. It is most commonly caused by infection, but may also be caused by overuse, diabetes and rheumatic conditions such as rheumatoid arthritis and crystal arthropathies. The present report describes two patients with severe proliferative tenosynovitis, who developed a fistula between the tendon sheath and skin after instrumentation, resulting in persistent synovial drainage. After failing conservative management, both patients were managed with extensive flexor tenosynovectomy to prevent inoculation of bacteria into the flexor sheath. The presentation, management and outcome of each case is described in addition to a discussion of the literature on tenosynovial fistulas. PMID:26090353

  11. The geometry and topology of natural sheath folds: a new tool for structural analysis

    NASA Astrophysics Data System (ADS)

    Alsop, G. I.; Holdsworth, R. E.

    2004-09-01

    Curvilinear sheath folds are classically depicted as displaying symmetrical geometries about two orthogonal mirror planes centred along the (X-Y) axial surface and the (X-Z) medial (culmination/depression) surface which bisects the fold nose. However, 10,000 geometric analyses of minor folds and fabrics formed during ductile thrusting in the Caledonides of northern Scotland reveals that major dome and basin sheath folds can display distinct and predictable asymmetries across both axial and medial surfaces. The strain is typically heterogeneous so that structural fabrics and younging evidence are preserved within sheath folds at varying stages of development. This allows an analysis of the evolution of such structures from 'tongue' folds to more extreme 'tubular' forms. Geometric relationships between measured orientations of fold hinges, axial planes, extension lineations and foliations are compared on fabric topology plots (FTPs), which provide an effective tool for monitoring planar and linear fabric rotations with increasing progressive non-coaxial deformation. They consistently display systematic variation from regions of lower to higher strain on passing from upper to lower fold limbs across major axial surfaces, and on crossing medial surfaces from short to long hinge-line segments. Axial and medial surfaces effectively therefore divide major sheath folds into quadrants with different amounts, senses and combinations of planar and linear fabric rotation within each domain. Such heterogeneous deformation implies that models of intense non-coaxial deformation uniformly affecting pre-existing folds may overestimate bulk displacement and shear strain. Variable fold hinge-line rotation about medial surfaces also provides an effective mechanism for the closure of major sheaths, which may otherwise project for unfeasible distances in the X direction. Bedding/cleavage intersections are developed at greater angles to the transport direction than fold hinges which they

  12. Numerical Model of the Plasma Sheath Generated by the Plasma Source Instrument Aboard the Polar Satellite

    NASA Technical Reports Server (NTRS)

    Leung, Wing C.; Singh, Nagendra; Moore, Thomas E.; Craven, Paul D.

    2000-01-01

    The plasma sheath generated by the operation of the Plasma Source Instrument (PSI) aboard the POLAR satellite is studied by using a 3-dimensional Particle-In-Cell (PIC) code. When the satellite passes through the region of low density plasma, the satellite charges to positive potentials as high as 4050Volts due to the photoelectrons emission. In such a case, ambient core ions cannot accurately be measured or detected. The goal of the onboard PSI is to reduce the floating potential of the satellite to a sufficiently low value so that the ions in the polar wind become detectable. When the PSI is operated, an ion-rich Xenon plasma is ejected from the satellite, such that the floating potential of the satellite is reduced and is maintained at about 2Volts. Accordingly, in our 3-dimensional PIC simulation, we considered that the potential of the satellite is 2Volts as a fixed bias. Considering the relatively high density of the Xenon plasma in the sheath (approx. 10 - 10(exp 3)/cc), the ambient plasma of low density (less than 1/cc) is neglected. In the simulations, the electric fields and plasma dynamics are calculated self-consistently. We found that an "Apple" shape positive potential sheath forms surrounding the satellite. In the region near the PSI emission, a high positive potential hill develops. Near the Thermal Ion Detection Experiment (TIDE) detector away from the PSI, the potentials are sufficiently low for the ambient polar wind ions to reach it. In the simulations, it takes about a hundred electron gyroperiods for the sheath to reach a quasi-steady state. This time is approximately the time taken by the heavy Xe(+) ions to expand up to about one average Larmor radius of electrons from the satellite surface. Using the steady state sheath, we performed trajectory calculations to characterize the detector response to a highly supersonic polar wind flow. The detected ions' velocity distribution shows significant deviations from a shifted Maxwellian in the

  13. Understanding the evolution and propagation of coronal mass ejections and associated plasma sheaths in interplanetary space

    NASA Astrophysics Data System (ADS)

    Hess, Phillip

    A Coronal Mass Ejection (CME) is an eruption of magnetized plasma from the Coronaof the Sun. Understanding the physical process of CMEs is a fundamental challenge in solarphysics, and is also of increasing importance for our technological society. CMEs are knownthe main driver of space weather that has adverse effects on satellites, power grids, com-munication and navigation systems and astronauts. Understanding and predicting CMEs is still in the early stage of research. In this dissertation, improved observational methods and advanced theoretical analysis are used to study CMEs. Unlike many studies in the past that treat CMEs as a single object, this study divides aCME into two separate components: the ejecta from the corona and the sheath region thatis the ambient plasma compressed by the shock/wave running ahead of the ejecta; bothstructures are geo-effective but evolve differently. Stereoscopic observations from multiplespacecraft, including STEREO and SOHO, are combined to provide a three-dimensionalgeometric reconstruction of the structures studied. True distances and velocities of CMEs are accurately determined, free of projection effects, and with continuous tracking from the low corona to 1 AU.To understand the kinematic evolution of CMEs, an advanced drag-based model (DBM) is proposed, with several improvements to the original DBM model. The new model varies the drag parameter with distance; the variation is constrained by thenecessary conservation of physical parameters. Second, the deviation of CME-nose from the Sun-Earth-line is taken into account. Third, the geometric correction of the shape of the ejecta front is considered, based on the assumption that the true front is a flattened croissant-shaped flux rope front. These improvements of the DBM model provide a framework for using measurement data to make accurate prediction of the arrival times of CME ejecta and sheaths. Using a set of seven events to test the model, it is found that the evolution

  14. Numerical solution of wave equations for the stability of the inner cometo-sheath

    NASA Technical Reports Server (NTRS)

    Srivastava, Krishna M.; Tsurutani, Bruce T.; Goldstein, Bruce E.

    1993-01-01

    Numerical solution of the MHD wave equations for stability of the cometary sheath determined by the balance between the inward Lorentz body force and the outward ion-neutral drag force is obtained by using a two-point boundary value method. The eigenvalues and the eigenfunctions are obtained numerically by treating the cometary inner sheath as a layer of finite thickness, bounded by the contact surface, i.e., the diamagnetic cavity boundary. The magnetic field structure discovered in the ionosphere of Comets Halley and Giacobini-Zinner is found to be unstable. The effects of finite plasma pressure, dissociative recombination, and mass loading due to photoionization are found to be stabilizing but are unable to quench the instability completely. It is also found that the higher the neutral production rate the lesser is the growth rate for the instability.

  15. Simple optics description of the plasma sheath and plasma electrode region

    SciTech Connect

    Fink, C.L.; Curry, B.P.

    1992-12-01

    A simple model of the optics of an ion source has been developed and compared with the exact Poisson solution calculated by computer code SNOW. The model replaces the Poisson potential by a Laplacian potential that is calculated by replacing the plasma and plasma sheath by a planar plate. This Laplacian potential is then used with and without a linear space-charge correction to calculate particle trajectories. In this model the only free parameter is the distance between the planar plate and the plasma electrode. In general, there is good agreement between emittance curves calculated by the model and the SNOW results even when no space-charge correction is used. This implies for the geometry we studied, that the effects of the plasma sheath and non-linear space-charge forces are small compared to aberrations introduced by the plasma aperture.

  16. Simple optics description of the plasma sheath and plasma electrode region

    SciTech Connect

    Fink, C.L.; Curry, B.P.

    1992-01-01

    A simple model of the optics of an ion source has been developed and compared with the exact Poisson solution calculated by computer code SNOW. The model replaces the Poisson potential by a Laplacian potential that is calculated by replacing the plasma and plasma sheath by a planar plate. This Laplacian potential is then used with and without a linear space-charge correction to calculate particle trajectories. In this model the only free parameter is the distance between the planar plate and the plasma electrode. In general, there is good agreement between emittance curves calculated by the model and the SNOW results even when no space-charge correction is used. This implies for the geometry we studied, that the effects of the plasma sheath and non-linear space-charge forces are small compared to aberrations introduced by the plasma aperture.

  17. Laboratory-experiments on shear-flow instabilities in a re-entry sheath

    NASA Astrophysics Data System (ADS)

    Niemann, C.; Ashour-Abdalla, M.; Clark, S. E.; Niehoff, D.; Schaeffer, D. B.; Constantin, C. G.; Schriver, D.; El Alaoui, M.; Sotnikov, V. I.

    2013-10-01

    Shear-flow instabilities in the plasma sheath surrounding re-entry vehicles and hypersonic aircraft can be detrimental to radio-communication but have not been investigated experimentally in detail. We present measurements of plasma-fluctuations in the lower-hybrid range, created in a laser-produced plasma plume that closely resembles a reentry sheath (1011-1013 cm-3, 1-20 eV). Shear-flow instabilities form in the diamagnetic current layer of the laser-produced plasma (20 J) exploding at hypersonic speed (M > 10) into a preformed magnetic field (400 G). Electric- and magnetic-field gradients are characterized with magnetic flux probes over large spatial (20 cm) and temporal scales, while the plasma parameters are measured via optical Thomson scattering. The frequency spectrum of plasma pulsations is investigated with biased Langmuir probes. The data is compared to simulations performed with a 2D PIC Darwin code. Work supported by the AFRL.

  18. Fibroma of the tendon sheath: A diagnostic dilemma on fine-needle aspiration cytology

    PubMed Central

    Nasit, Jitendra G; Dhruva, Gauravi

    2015-01-01

    Fibroma of the tendon sheath (FTS) is an uncommon benign soft tissue tumor (STS) of the tendon sheath. Clinical and radiological features are not distinctive enough to clinch the diagnosis preoperatively. Although histological features are well described, diagnostic cytological features of FTS are still lacking. Till date only two reports describe the fine-needle aspiration cytology (FNAC) findings of FTS. The present case is a 50-year-old female who presented with a slow growing nodule on the right thigh over a period of 2 years. FNAC revealed low cell yield with loose clusters of fibrotic spindle cells and stellate cells intermingled with fibro-collagenous and myxoid matrix. Few cells showed mild degree of nuclear atypia. Necrosis and atypical mitoses were not seen. Cytology findings were suggestive of benign/low-grade fibroblastic or fibromyxoid lesion. Histology confirmed the diagnosis of FTS. This article discusses the diagnostic role of FNAC in FTS with its differential diagnosis PMID:26729987

  19. Differential positioning of chloroplasts in C4 mesophyll and bundle sheath cells.

    PubMed

    Maai, Eri; Miyake, Hiroshi; Taniguchi, Mitsutaka

    2011-08-01

    Chloroplast photorelocation movement is extensively studied in C3 but not C4 plants. C4 plants have 2 types of photosynthetic cells: mesophyll and bundle sheath cells. Mesophyll chloroplasts are randomly distributed along cell walls, whereas bundle sheath chloroplasts are located close to the vascular tissues or mesophyll cells depending on the plant species. The cell-specific C 4 chloroplast arrangement is established during cell maturation, and is maintained throughout the life of the cell. However, only mesophyll chloroplasts can change their positions in response to environmental stresses. The migration pattern is unique to C4 plants and differs from that of C3 chloroplasts. In this mini-review, we highlight the cell-specific disposition of chloroplasts in C4 plants and discuss the possible physiological significances.

  20. Valid flow combinations for stable sheath in a magnetized multiple ion species plasma

    SciTech Connect

    Sharma, Devendra; Kaw, Predhiman K.

    2012-11-15

    Theoretical study is done of the entry criterion for the plasma flow into the electrostatic boundary layer, or sheath, forming in a magnetized multiple ion species plasma. Finding valid entry velocity combinations in a magnetized set up requires a magnetized equivalent of the generalized Bohm criterion. A magnetized generalized entry criterion is obtained with the scale length distribution in a region of validity for the stable solutions. The analysis finds that the valid entry flow velocity combinations with distinct values of individual ion species can correspond to a unique system phase velocity. Magnetization effects govern the region of validity whose boundaries collapse to the unmagnetized sheath criterion in the limit of normal incidence, independent of the strength of the magnetic field. Considerably smaller entry velocities, in comparison to the unmagnetized system sound velocity, are recovered for the species in appropriate regime of magnetization in the cases of oblique incidences.

  1. Generalized Redox-Responsive Assembly of Carbon-Sheathed Metallic and Semiconducting Nanowire Heterostructures.

    PubMed

    Choi, Sinho; Kim, Jieun; Hwang, Dae Yeon; Park, Hyungmin; Ryu, Jaegeon; Kwak, Sang Kyu; Park, Soojin

    2016-02-10

    One-dimensional metallic/semiconducting materials have demonstrated as building blocks for various potential applications. Here, we report on a unique synthesis technique for redox-responsive assembled carbon-sheathed metal/semiconducting nanowire heterostructures that does not require a metal catalyst. In our approach, germanium nanowires are grown by the reduction of germanium oxide particles and subsequent self-catalytic growth during the thermal decomposition of natural gas, and simultaneously, carbon sheath layers are uniformly coated on the nanowire surface. This process is a simple, reproducible, size-controllable, and cost-effective process whereby most metal oxides can be transformed into metallic/semiconducting nanowires. Furthermore, the germanium nanowires exhibit stable chemical/thermal stability and outstanding electrochemical performance including a capacity retention of ∼96% after 1200 cycles at the 0.5-1C rate as lithium-ion battery anode. PMID:26784743

  2. Shear flow instability in a partially-ionized plasma sheath around a fast-moving vehicle

    SciTech Connect

    Sotnikov, V. I.; Mudaliar, S.; Genoni, T. C.; Rose, D. V.; Oliver, B. V.; Mehlhorn, T. A.

    2011-06-15

    The stability of ion acoustic waves in a sheared-flow, partially-ionized compressible plasma sheath around a fast-moving vehicle in the upper atmosphere, is described and evaluated for different flow profiles. In a compressible plasma with shear flow, instability occurs for any velocity profile, not just for profiles with an inflection point. A second-order differential equation for the electrostatic potential of excited ion acoustic waves in the presence of electron and ion collisions with neutrals is derived and solved numerically using a shooting method with boundary conditions appropriate for a finite thickness sheath in contact with the vehicle. We consider three different velocity flow profiles and find that in all cases that neutral collisions can completely suppress the instability.

  3. A joint computational and experimental study to evaluate Inconel-sheathed thermocouple performance in flames.

    SciTech Connect

    Brundage, Aaron L.; Nicolette, Vernon F.; Donaldson, A. Burl; Kearney, Sean Patrick; Gill, Walter

    2005-09-01

    A joint experimental and computational study was performed to evaluate the capability of the Sandia Fire Code VULCAN to predict thermocouple response temperature. Thermocouple temperatures recorded by an Inconel-sheathed thermocouple inserted into a near-adiabatic flat flame were predicted by companion VULCAN simulations. The predicted thermocouple temperatures were within 6% of the measured values, with the error primarily attributable to uncertainty in Inconel 600 emissivity and axial conduction losses along the length of the thermocouple assembly. Hence, it is recommended that future thermocouple models (for Inconel-sheathed designs) include a correction for axial conduction. Given the remarkable agreement between experiment and simulation, it is recommended that the analysis be repeated for thermocouples in flames with pollutants such as soot.

  4. Plasma wall sheath contributions to flux retention during the formation of field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Milroy, R. D.; Slough, J. T.; Hoffman, A. L.

    1984-06-01

    Flux loss during field reversal on the TRX-1 field-reversed θ pinch is found to be much less than predicted by the inertial model of Green and Newton. This can be explained by a pressure bearing, conducting sheath which naturally forms at the wall and limits the flux loss. A one-dimensional (r-t) magnetohydrodynamic (MHD) numerical model has been used to study the formation and effectiveness of the sheath. The calculations are in excellent agreement with experimental measurements over a wide range of operating parameters. The results indicate that good flux trapping can be achieved through the field reversal phase of FRC formation with much slower external field reversal rates than in current experiments.

  5. Collisionless “thermalization” in the sheath of an argon discharge

    SciTech Connect

    Coulette, David Manfredi, Giovanni

    2015-04-15

    We performed kinetic Vlasov simulations of the plasma-wall transition for a low-pressure argon discharge without external magnetic fields, using the same plasma parameters as in the experiments of Claire et al. [Phys. Plasmas 13, 062103 (2006)]. Experimentally, it was found that the ion velocity distribution function is highly asymmetric in the presheath, but, surprisingly, becomes again close to Maxwellian inside the sheath. Here, we show that this “thermalization” can be explained by purely collisionless effects that are akin to the velocity bunching phenomenon observed in charged particles beams. Such collisionless thermalization is also observed in the presheath region close to the sheath entrance, although it is much weaker there and in practice probably swamped by collisional processes (standard or enhanced by instabilities)

  6. Pyramiding transgenes for multiple resistance in rice against bacterial blight, yellow stem borer and sheath blight.

    PubMed

    Datta, K; Baisakh, N; Thet, K Maung; Tu, J; Datta, S K

    2002-12-01

    Here we describe the development of transgene-pyramided stable elite rice lines resistant to disease and insect pests by conventional crossing of two transgenic parental lines transformed independently with different genes. The Xa21 gene (resistance to bacterial blight), the Bt fusion gene (for insect resistance) and the chitinase gene (for tolerance of sheath blight) were combined in a single rice line by reciprocal crossing of two transgenic homozygous IR72 lines. F4 plant lines carrying all the genes of interest stably were identified using molecular methods. The identified lines, when exposed to infection caused by Xanthomonas oryzae pv oryzae, showed resistance to bacterial blight. Neonate larval mortality rates of yellow stem borer ( Scirpophaga incertulas) in an insect bioassay of the same identified lines were 100%. The identified line pyramided with different genes to protect against yield loss showed high tolerance of sheath blight disease caused by Rhizoctonia solani.

  7. Ion velocity distributions in the sheath and presheath of a biased object in plasma

    SciTech Connect

    Miloch, W. J.; Gulbrandsen, N.; Mishra, L. N.; Fredriksen, A.

    2011-08-15

    Ion velocity distributions in the vicinity of a spherical object with a negative potential with respect to collisionless, source-free plasma are studied with three-dimensional numerical simulations. The ion dynamics around the object leads to distorted radial velocity distributions in the presheath and the sheath edge region. Far in the sheath, an increase in the thermal velocity in the radial direction is observed. Different potentials of the object, ion temperatures, and ion masses are considered, as well as the role of spatial and temporal resolutions in laboratory measurements of ion velocity distributions. The simulations are carried out with the DiP3D, a three-dimensional particle-in-cell numerical code.

  8. Extracted hair follicle outer root sheath cell suspension for pigment cell restoration in vitiligo.

    PubMed

    Kumar, Anil; Mohanty, Sujata; Sahni, Kanika; Kumar, Rajesh; Gupta, Somesh

    2013-04-01

    Vitiligo surgery has come up a long way from punch skin grafts to epidermal cell suspension and latest to the extracted hair follicle outer root sheath cell suspension (EHF-ORS-CS) transplantation. The progressive development from one technique to the other is always in a quest for the best. In the latest development- EHF-ORS-CS, which is an enriched source of follicular inactive melanocyte (melanocyte stem cells), seems to be a good addition to the prevailing cell-based therapies for vitiligo; however, need to be explored further in larger, and preferably randomized blinded studies. This review discusses the principle, technical details, and stem cell composition of hair follicular outer root sheath cell suspension. PMID:24023440

  9. Installing Windows with Foam Sheathing on a Wood-Frame Wall: January 1, 2004 to December 31, 2004

    SciTech Connect

    2005-05-01

    In most wall assemblies, connection details around windows have been the source of problems with water penetration into the building. This report describes how to install a window into a wall with insulating sheathing as an integrated drainage plane.

  10. Synthesis of carbon nanotubes/Si nanowires core-sheath structure arrays and their field emission properties

    NASA Astrophysics Data System (ADS)

    Lu, M.; Li, M. K.; Zhang, Z. J.; Li, H. L.

    2003-09-01

    A new composite structure of carbon nanotubes (CNTs)/Si nanowires (SiNWs) arrays have been synthesized by chemical vapor deposition (CVD) within the pores of microporous alumina template. The results of scanning electron microscopy (SEM) and transmission electron microcopy (TEM) reveal that the obtained well-aligned composite structure has a core-sheath structure and the deposited material in the carbon sheath is polycrystalline silicon. Field emission from these CNTs-sheathed SiNWs exhibits significant enhancement compared to the pure SiNWs in turn-on field, total emission current and stability. The field emission characteristics of the composite structure are analyzed based on Fowler-Nordheim theory. The electron field emission increased with decreasing diameter of such structure. The well-aligned core-sheath structure provides an important means to fabricate emitter devices with chemically inert surface as well as with superior performance of field emission properties.

  11. Bounds imposed on the sheath velocity of a dense plasma focus by conservation laws and ionization stability condition

    SciTech Connect

    Auluck, S. K. H. E-mail: skauluck@barc.gov.in

    2014-09-15

    Experimental data compiled over five decades of dense plasma focus research are consistent with the snowplow model of sheath propagation, based on the hypothetical balance between magnetic pressure driving the plasma into neutral gas ahead and “wind pressure” resisting its motion. The resulting sheath velocity, or the numerically proportional “drive parameter,” is known to be approximately constant for devices optimized for neutron production over 8 decades of capacitor bank energy. This paper shows that the validity of the snowplow hypothesis, with some correction, as well as the non-dependence of sheath velocity on device parameters, have their roots in local conservation laws for mass, momentum, and energy coupled with the ionization stability condition. Both upper and lower bounds on sheath velocity are shown to be related to material constants of the working gas and independent of the device geometry and capacitor bank impedance.

  12. Bounds imposed on the sheath velocity of a dense plasma focus by conservation laws and ionization stability condition

    NASA Astrophysics Data System (ADS)

    Auluck, S. K. H.

    2014-09-01

    Experimental data compiled over five decades of dense plasma focus research are consistent with the snowplow model of sheath propagation, based on the hypothetical balance between magnetic pressure driving the plasma into neutral gas ahead and "wind pressure" resisting its motion. The resulting sheath velocity, or the numerically proportional "drive parameter," is known to be approximately constant for devices optimized for neutron production over 8 decades of capacitor bank energy. This paper shows that the validity of the snowplow hypothesis, with some correction, as well as the non-dependence of sheath velocity on device parameters, have their roots in local conservation laws for mass, momentum, and energy coupled with the ionization stability condition. Both upper and lower bounds on sheath velocity are shown to be related to material constants of the working gas and independent of the device geometry and capacitor bank impedance.

  13. Modeling of and experiments on dust particle levitation in the sheath of a radio frequency plasma reactor

    SciTech Connect

    Setyawan, Heru; Shimada, Manabu; Hayashi, Yutaka; Okuyama, Kikuo; Winardi, Sugeng

    2005-02-15

    The equilibrium and trapping of dust particles in a plasma sheath are investigated, both experimentally and theoretically. A self-consistent sheath model including input power as one of the model parameters is proposed, to predict the equilibrium position of particle trap. The electron temperature and density are estimated from the observed current and power (I-P) characteristics using the sheath model developed. Direct comparisons are made between the measured equilibrium position and the predicted equilibrium position. The equilibrium position moves closer to the electrode with increasing rf power and particle size. The position is apparently related to the sheath thickness, which decreases with increasing rf power. The model can correctly predict the experimentally observed trend in the equilibrium position of particle trap. It is found that the particle charge becomes positive when the particle gets closer to the electrode, due to the dominant influence of ion currents to the particle surface.

  14. Numerical investigation of the ion temperature effect in magnetized plasma sheath with two species of positive ions

    SciTech Connect

    Shaw, A. K.; Goswami, K. S.; Saikia, B. J.; Kar, S.

    2012-01-15

    The effect of ion temperature, magnitude of magnetic field and its orientation on a magnetized plasma sheath consisting of electrons and two species of positive ions are investigated. Using three-fluid hydrodynamic model and some dimensionless variables, the dimensionless equations are obtained and solved numerically. It is found that with the increase of the ion temperature and magnetic field strength there is a significant change in ion densities and energies in the sheath. It is also noticed that increase of magnetic field angle enhances the ion density near the sheath edge for a constant ion temperature. With increase in ion temperature and magnetic field angle, the lighter ion density near the sheath edge enhances and reverses for the heavier ion species.

  15. Space Charge Saturated Sheath Regime and Electron Temperature Saturation in Hall Thrusters

    SciTech Connect

    Y. Raitses; D. Staack; A. Smirnov; N.J. Fisch

    2005-03-16

    Secondary electron emission in Hall thrusters is predicted to lead to space charge saturated wall sheaths resulting in enhanced power losses in the thruster channel. Analysis of experimentally obtained electron-wall collision frequency suggests that the electron temperature saturation, which occurs at high discharge voltages, appears to be caused by a decrease of the Joule heating rather than by the enhancement of the electron energy loss at the walls due to a strong secondary electron emission.

  16. Sheathed thermocouples for continuous molten steel temperature measurement during the ladle treatment process

    SciTech Connect

    Phillippi, R.M. . Accumetrix Div.)

    1989-09-01

    The evolution of a thermocouple protection sheath for use in liquid steel during the ladle treatment process is described. Five different designs constructed of boron nitride, alumina-graphite, and magnesia-graphite were evaluated. Results show that excellent slag wear characteristics are possible using magnesia-graphite but improvements in thermal shock resistance and response time are required. Temperature profiles during argon stirring, addition of chill scrap, and natural cooling are presented. 3 refs., 19 figs.

  17. Purification and Properties of an Enzyme Capable of Degrading the Sheath of Sphaerotilus natans

    PubMed Central

    Takeda, Minoru; Iohara, Keishi; Shinmaru, Sachie; Suzuki, Ichiro; Koizumi, Jun-Ichi

    2000-01-01

    Microorganisms which can degrade and grow on the purified sheath of a sheathed bacterium Sphaerotilus natans were collected from soil and river water. Two bacterial strains were isolated from the soil and designated strains TB and TK. Both strains are rod shaped, negatively stained by gram staining, facultatively anaerobic, and formed ellipsoidal endospores. These characteristics suggested that the isolates belong to the genus Paenibacillus, according to Ash et al. (C. Ash, F. G. Priest, and M. D. Collins, Antonie Leeuwenhoek 64:253–260, 1993). Phylogenetic analysis based on the 16S rDNA supported this possibility. Purification of the sheath-degrading enzyme was carried out from the culture broth of strain TB. The molecular weight of the enzyme was calculated to be 78,000 and 50,000 by sodium dodecyl sulfate-polyacrylamide electrophoresis and gel filtration chromatography, respectively. Enzyme activity was optimized at pH 6.5 to 7.0 and 30 to 40°C. The reaction was accelerated by the addition of Mg2+, Ca2+, Fe3+, and iodoacetamide, whereas it was inhibited by the addition of Cu2+, Mn2+, and dithiothreitol. The enzyme acted on the polysaccharide moiety of the sheath, producing an oligosaccharide the size of which was between the sizes of maltopentaose and maltohexaose. As the reaction proceeded, the absorbance at 235 nm of the reaction mixture increased, suggesting the generation of unsaturated sugars. Incorporation of unsaturated sugars was also suggested by the thiobarbituric acid reaction. It is possible that the enzyme is not a hydrolytic enzyme but a kind of polysaccharide eliminase which acts on the basic polysaccharide. PMID:11055955

  18. Solar wind-magnetosphere coupling efficiency during ejecta and sheath-driven geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Myllys, M.; Kilpua, E. K. J.; Lavraud, B.; Pulkkinen, T. I.

    2016-05-01

    We have investigated the effect of key solar wind driving parameters on solar wind-magnetosphere coupling efficiency during sheath and magnetic cloud-driven storms. The particular focus of the study was on the coupling efficiency dependence with Alfvén Mach number (MA). The efficiency has been estimated using the dawn-dusk component of the interplanetary electric field (EY), Newell and Borovsky functions as a proxy for the energy inflow and the polar cap potential (PCN), and auroral electrojet (AE) and SYM-H indices as the measure of the energy output. We have also performed a time delay analysis between the input parameters and the geomagnetic indices. The optimal time lag and smoothing window length depend on the coupling function used and on the solar wind driver. For example, turbulent sheaths are more sensitive to the time shift and the averaging interval than smoother magnetic clouds. The results presented in this study show that the solar wind-magnetosphere coupling efficiency depends strongly on the definition used, and it increases with increasing MA. We demonstrate that the PCN index distinctively shows both a Mach number dependent saturation and a Mach number independent saturation, pointing to the existence of at least two underlying physical mechanisms for the saturation of the index. By contrast, we show that the AE index saturates but that the saturation of this index is independent of the solar wind Mach number. Finally, we find that the SYM-H index does not seem to saturate and that the absence of saturation is independent of the Mach number regime. We highlight the difference between the typical MA conditions during sheath regions and magnetic clouds. The lowest MA values are related to the magnetic clouds. As a consequence, sheaths typically have higher solar wind-magnetosphere coupling efficiencies than magnetic clouds.

  19. Deep crustal deformation by sheath folding in the Adirondack Mountains, USA

    NASA Technical Reports Server (NTRS)

    Mclelland, J. M.

    1988-01-01

    As described by McLelland and Isachsen, the southern half of the Adirondacks are underlain by major isoclinal (F sub 1) and open-upright (F sub 2) folds whose axes are parallel, trend approximately E-W, and plunge gently about the horizontal. These large structures are themselves folded by open upright folds trending NNE (F sub 3). It is pointed out that elongation lineations in these rocks are parallel to X of the finite strain ellipsoid developed during progressive rotational strain. The parallelism between F sub 1 and F sub 2 fold axes and elongation lineations led to the hypothesis that progressive rotational strain, with a west-directed tectonic transport, rotated earlier F sub 1-folds into parallelism with the evolving elongation lineation. Rotation is accomplished by ductile, passive flow of F sub 1-axes into extremely arcuate, E-W hinges. In order to test these hypotheses a number of large folds were mapped in the eastern Adirondacks. Other evidence supporting the existence of sheath folds in the Adirondacks is the presence, on a map scale, of synforms whose limbs pass through the vertical and into antiforms. This type of outcrop pattern is best explained by intersecting a horizontal plane with the double curvature of sheath folds. It is proposed that sheath folding is a common response of hot, ductile rocks to rotational strain at deep crustal levels. The recognition of sheath folds in the Adirondacks reconciles the E-W orientation of fold axes with an E-W elongation lineation.

  20. Optic nerve sheath fenestration for the treatment of papilledema secondary to cerebral venous thrombosis.

    PubMed

    Murdock, Jennifer; Tzu, Jonathan H; Schatz, Norman J; Lee, Wendy W

    2014-03-01

    A 16-year-old adolescent girl with multiple risk factors for thrombosis presented with acute onset of headache, decreased vision, and papilledema. Evaluation demonstrated cerebral venous thrombosis (CVT) involving the left transverse and sigmoid sinuses and left internal jugular vein. Following bilateral optic nerve sheath fenestration (ONSF), she experienced improvement in vision and resolution of papilledema. In selected cases, ONSF is an effective surgical option for the treatment of papilledema due to CVT after medical treatment has failed. PMID:24343230

  1. Release of celecoxib from a bi-layer biomimetic tendon sheath to prevent tissue adhesion.

    PubMed

    Li, Laifeng; Zheng, Xianyou; Fan, Dapeng; Yu, Shiyang; Wu, Di; Fan, Cunyi; Cui, Wenguo; Ruan, Hongjiang

    2016-04-01

    Posttraumatic tendon adhesion limits the motion of the limbs greatly. Biomimetic tendon sheaths have been developed to promote tendon healing and gliding. However, after introduction of these biomaterials, the associated inflammatory responses can decrease the anti-adhesion effect. Celecoxib is a non-steroidal anti-inflammatory drug (NSAID) that can decrease inflammation responses. We blended hyaluronic acid and poly(l-lactic acid)-polyethylene glycol (PELA) with microgel electrospinning technology to form an inner layer of a bi-layer biomimetic sheath using sequential electrospinning of an outer celecoxib-PELA layer. Electrospun bi-layer fibrous membranes were mechanically tested and characterized by morphology, surface wettability, and drug release. The tensile strength showed a decreased trend and water contact angles were 114.7 ± 3.9°, 103.6 ± 4.4°, 116.3 ± 5.1°, 122.8 ± 4.7°, and 126.5 ± 4.2° for the surface of PELA, hyaluronic acid-PELA, 2, 6, and 10% celecoxib-PELA electrospun fibrous membranes, respectively. In vitro drug release studies confirmed burst release and then sustained release from the fibrous membranes containing celecoxib for 20 days. In a chicken model of flexor digitorum profundus tendon surgery, the outer celecoxib/PELA layer offered advanced anti-adhesion roles compared to the outer PELA layer and the inner hyaluronic acid-loaded PELA layer still offered tendon healing and gliding. Thus, celecoxib-loaded anti-adhesive tendon sheaths can continuously offer bi-layer biomimetic tendon sheath effects with celecoxib release from the outer layer to prevent tendon adhesion. PMID:26838844

  2. Including sheath effects in the interpretation of planar retarding potential analyzer's low-energy ion data.

    PubMed

    Fisher, L E; Lynch, K A; Fernandes, P A; Bekkeng, T A; Moen, J; Zettergren, M; Miceli, R J; Powell, S; Lessard, M R; Horak, P

    2016-04-01

    The interpretation of planar retarding potential analyzers (RPA) during ionospheric sounding rocket missions requires modeling the thick 3D plasma sheath. This paper overviews the theory of RPAs with an emphasis placed on the impact of the sheath on current-voltage (I-V) curves. It then describes the Petite Ion Probe (PIP) which has been designed to function in this difficult regime. The data analysis procedure for this instrument is discussed in detail. Data analysis begins by modeling the sheath with the Spacecraft Plasma Interaction System (SPIS), a particle-in-cell code. Test particles are traced through the sheath and detector to determine the detector's response. A training set is constructed from these simulated curves for a support vector regression analysis which relates the properties of the I-V curve to the properties of the plasma. The first in situ use of the PIPs occurred during the MICA sounding rocket mission which launched from Poker Flat, Alaska in February of 2012. These data are presented as a case study, providing valuable cross-instrument comparisons. A heritage top-hat thermal ion electrostatic analyzer, called the HT, and a multi-needle Langmuir probe have been used to validate both the PIPs and the data analysis method. Compared to the HT, the PIP ion temperature measurements agree with a root-mean-square error of 0.023 eV. These two instruments agree on the parallel-to-B plasma flow velocity with a root-mean-square error of 130 m/s. The PIP with its field of view aligned perpendicular-to-B provided a density measurement with an 11% error compared to the multi-needle Langmuir Probe. Higher error in the other PIP's density measurement is likely due to simplifications in the SPIS model geometry. PMID:27131671

  3. Optic Nerve Sheath as a Novel Mechanical Load on the Globe in Ocular Duction

    PubMed Central

    Demer, Joseph L.

    2016-01-01

    Purpose The optic nerve (ON) sheath's role in limiting duction has been previously unappreciated. This study employed magnetic resonance imaging (MRI) to demonstrate this constraint on adduction. Methods High-resolution, surface coil axial MRI was obtained in 11 normal adults, 14 subjects with esotropia (ET) having normal axial length (AL) < 25.8 mm, 13 myopic subjects with ET and mean AL 29.3 ± 3.3 (SD) mm, and 7 subjects with exotropia (XT). Gaze angles and ON lengths were measured for scans employing eccentric lateral fixation in which an ON became completely straightened. Results In all groups, ON straightening occurred only in the adducting, not abducting, eye. Adduction at ON straightening was 26.0 ± 8.8° in normal subjects, not significantly different from XT at 22.2 ± 11.8°. However, there was significant increase in comparable adduction in ET to 36.3 ± 9.3°, and in myopic ET to 33.6 ± 10.7° (P < 0.04). Optic nerve length at straightening was 27.6 ± 2.7 mm in normals, not significantly different from 28.2 ± 2.8 mm in ET and 27.8 ± 2.7 mm in XT. In myopic ET, ON length at straightening was significantly reduced to 24.0 ± 2.9 mm (P < 0.002) and was associated with globe retraction in adduction, suggesting ON tethering. Conclusions Large adduction may exhaust length redundancy in the normally sinuous ON and sheath, so that additional adduction must stretch the sheath and retract or deform the globe. These mechanical effects are most significant in ET with axial myopia, but may also exert traction on the posterior sclera absent strabismus or myopia. Tethering by the ON sheath in adduction is an important, novel mechanical load on the globe. PMID:27082297

  4. Mechanical characterisation of porcine rectus sheath under uniaxial and biaxial tension.

    PubMed

    Lyons, Mathew; Winter, Des C; Simms, Ciaran K

    2014-06-01

    Incisional hernia development is a significant complication after laparoscopic abdominal surgery. Intra-abdominal pressure (IAP) is known to initiate the extrusion of intestines through the abdominal wall, but there is limited data on the mechanics of IAP generation and the structural properties of rectus sheath. This paper presents an explanation of the mechanics of IAP development, a study of the uniaxial and biaxial tensile properties of porcine rectus sheath, and a simple computational investigation of the tissue. Analysis using Laplace׳s law showed a circumferential stress in the abdominal wall of approx. 1.1MPa due to an IAP of 11kPa, commonly seen during coughing. Uniaxial and biaxial tensile tests were conducted on samples of porcine rectus sheath to characterise the stress-stretch responses of the tissue. Under uniaxial tension, fibre direction samples failed on average at a stress of 4.5MPa at a stretch of 1.07 while cross-fibre samples failed at a stress of 1.6MPa under a stretch of 1.29. Under equi-biaxial tension, failure occurred at 1.6MPa with the fibre direction stretching to only 1.02 while the cross-fibre direction stretched to 1.13. Uniaxial and biaxial stress-stretch plots are presented allowing detailed modelling of the tissue either in silico or in a surrogate material. An FeBio computational model of the tissue is presented using a combination of an Ogden and an exponential power law model to represent the matrix and fibres respectively. The structural properties of porcine rectus sheath have been characterised and add to the small set of human data in the literature with which it may be possible to develop methods to reduce the incidence of incisional hernia development. PMID:24725440

  5. Formation of double sheaths and the J-V characteristics of the obstructed region

    SciTech Connect

    Wang, C.C.

    1980-06-01

    The arc drop of the vapor thermionic converter is determined by the difference of sheath heights and the potential difference across the plasma. The J-V characteristics of cesium vapor diodes operating in the ignited mode show a knee corresponding to near optimum power. When the diode is operating in the region above the knee, the dominant contributor to the arc drop is the difference of the sheath heights (i.e., the potential difference across the plasma produces either a very small loss or may, in fact, reverse sign and reduce the arc drop). In this region the power decreases because the increase in output current is usually not able to compensate for the loss of output voltage. When the diode is operating in the region below the knee, the potential difference in the plasma becomes the dominant contributor to the arc drop. For these reasons, the shape of the J-V characteristics below the knee is different from that above the knee. The location of the knee is a good indicator of the maximum power and the maximum efficiency points. Under the fully optimized conditions, the knee also indicates the barrier index of the diode. Therefore, how and where the knee will appear is of great theoretical and practical interest. Some workers in the thermionic field have speculated that the appearance of the knee is due to the formation of the double sheath. However, this study indicates that the formation of the double sheath takes place significantly below the knee. In addition, this study evaluates J-V characteristics in the obstructed region.

  6. Lost in Translation: Ambiguity in Nerve Sheath Tumor Nomenclature and Its Resultant Treatment Effect

    PubMed Central

    Bernthal, Nicholas M.; Jones, Kevin B.; Monument, Michael J.; Liu, Ting; Viskochil, David; Randall, R. Lor

    2013-01-01

    There is much ambiguity surrounding the diagnosis of nerve sheath tumors, including atypical neurofibroma and low-grade MPNST, and yet, the distinction between these entities designates either benign or malignant behavior and thus carries presumed profound prognostic importance that often guides treatment. This study reviews the diagnostic criteria used to designate atypical neurofibroma from low-grade MPNSTs and reviews existing literature the natural history of each of these tumors to see if the distinction is, in fact, of importance. PMID:24216989

  7. Generation of dust projectiles passing over an obstacle in the plasma sheath

    SciTech Connect

    Ticos, Catalin M.; Stoica, Daniel S.; Delzanno, Gian Luca

    2012-08-15

    Dust projectiles were produced in a radio-frequency plasma by increasing 6-fold the radio-frequency power put into the discharge. The initial static dust particles were observed to gain speed while moving away from the confining region and escaped from the inter-electrode space on a ballistic-like trajectory. Single-grain dynamics simulations indicated that the dust particles were accelerated by changes induced in the sheath electric field profile.

  8. The Plasma-Sheath Boundary in Two-Ion-Species Plasmas

    NASA Astrophysics Data System (ADS)

    Baalrud, Scott D.

    2014-10-01

    The Bohm criterion is among the most important results in plasma physics because it provides the ion flow speed at the sheath edge under common plasma conditions. This is a useful boundary condition for modeling plasma-materials interactions, as well as for global plasma models. However, a difficulty arises when multiple ion species are present because the Bohm criterion provides only one constraint in as many unknowns as there are ion species. Conventional theory assumes that the ion species are decoupled, which leads to the prediction that each obtains its individual sound speed at the sheath edge: Vi =√{Te /mi } . However, experiments in Ar-Xe and He-Xe mixtures have revealed that the ion speeds can merge toward a common speed under typical low-temperature plasma conditions. This merging of ion speeds suggests that ion-ion friction may be playing a role, but standard Coulomb collisions are far too weak to explain the measurements. In this work, we discuss how the experimental results can be understood by accounting for wave-particle collisions from ion-ion two-stream instabilities. These instabilities arise when the differential flow speed between the ion species exceeds a threshold value that depends on the ion species concentrations and the electron-ion temperature ratio. When this threshold is exceeded, wave-particle interactions rapidly increase the collision rate leading to an ion-ion friction force that effectively ``locks'' the differential flow speed to the instability threshold. This provides a second constraint that can be used to determine the speed of each ion species at the sheath edge. We present numerical calculations of the instability threshold, and new particle-in-cell simulations that show the presence of both the instabilites and enhanced friction force. Only by accounting for the instabilites can theory predict the simulated ion speeds at the sheath edge. Work supported by the University of Iowa, and the USDOE Fusion Energy Sciences

  9. Dynamics of auxin movement in the gravistimulated leaf-sheath pulvinus of oat (Avena sativa)

    NASA Technical Reports Server (NTRS)

    Brock, Thomas C.; Kapen, E. H.; Ghosheh, Najati S.; Kaufman, Peter B.

    1991-01-01

    The role of auxin redistribution in the graviresponse of the leaf-sheath pulvinus of oat was evaluated using H-3-indole-3-acetic acid (H-3-IAA) preloaded into isolated pulvini. Results obtained reveal that, while lateral transport of auxin occurs following gravistimulation, it is not necessary for a graviresponse. Localized changes in tissue responsiveness or the conversion of conjugated hormone to free hormone may suffice to drive the graviresponse.

  10. Lost in translation: ambiguity in nerve sheath tumor nomenclature and its resultant treatment effect.

    PubMed

    Bernthal, Nicholas M; Jones, Kevin B; Monument, Michael J; Liu, Ting; Viskochil, David; Randall, R Lor

    2013-05-08

    There is much ambiguity surrounding the diagnosis of nerve sheath tumors, including atypical neurofibroma and low-grade MPNST, and yet, the distinction between these entities designates either benign or malignant behavior and thus carries presumed profound prognostic importance that often guides treatment. This study reviews the diagnostic criteria used to designate atypical neurofibroma from low-grade MPNSTs and reviews existing literature the natural history of each of these tumors to see if the distinction is, in fact, of importance.

  11. Including sheath effects in the interpretation of planar retarding potential analyzer's low-energy ion data

    NASA Astrophysics Data System (ADS)

    Fisher, L. E.; Lynch, K. A.; Fernandes, P. A.; Bekkeng, T. A.; Moen, J.; Zettergren, M.; Miceli, R. J.; Powell, S.; Lessard, M. R.; Horak, P.

    2016-04-01

    The interpretation of planar retarding potential analyzers (RPA) during ionospheric sounding rocket missions requires modeling the thick 3D plasma sheath. This paper overviews the theory of RPAs with an emphasis placed on the impact of the sheath on current-voltage (I-V) curves. It then describes the Petite Ion Probe (PIP) which has been designed to function in this difficult regime. The data analysis procedure for this instrument is discussed in detail. Data analysis begins by modeling the sheath with the Spacecraft Plasma Interaction System (SPIS), a particle-in-cell code. Test particles are traced through the sheath and detector to determine the detector's response. A training set is constructed from these simulated curves for a support vector regression analysis which relates the properties of the I-V curve to the properties of the plasma. The first in situ use of the PIPs occurred during the MICA sounding rocket mission which launched from Poker Flat, Alaska in February of 2012. These data are presented as a case study, providing valuable cross-instrument comparisons. A heritage top-hat thermal ion electrostatic analyzer, called the HT, and a multi-needle Langmuir probe have been used to validate both the PIPs and the data analysis method. Compared to the HT, the PIP ion temperature measurements agree with a root-mean-square error of 0.023 eV. These two instruments agree on the parallel-to-B plasma flow velocity with a root-mean-square error of 130 m/s. The PIP with its field of view aligned perpendicular-to-B provided a density measurement with an 11% error compared to the multi-needle Langmuir Probe. Higher error in the other PIP's density measurement is likely due to simplifications in the SPIS model geometry.

  12. Structural characterization of the human cerebral myelin sheath by small angle x-ray scattering.

    PubMed

    De Felici, M; Felici, R; Ferrero, C; Tartari, A; Gambaccini, M; Finet, S

    2008-10-21

    Myelin is a multi-lamellar membrane surrounding neuronal axons and increasing their conduction velocity. When investigated by small-angle x-ray scattering (SAXS), the lamellar quasi-periodical arrangement of the myelin sheath gives rise to distinct peaks, which allow the determination of its molecular organization and the dimensions of its substructures. In this study we report on the myelin sheath structural determination carried out on a set of human brain tissue samples coming from surgical biopsies of two patients: a man around 60 and a woman nearly 90 years old. The samples were extracted either from white or grey cerebral matter and did not undergo any manipulation or chemical-physical treatment, which could possibly have altered their structure, except dipping them into a formalin solution for their conservation. Analysis of the scattered intensity from white matter of intact human cerebral tissue allowed the evaluation not only of the myelin sheath periodicity but also of its electronic charge density profile. In particular, the thicknesses of the cytoplasm and extracellular regions were established, as well as those of the hydrophilic polar heads and hydrophobic tails of the lipid bilayer. SAXS patterns were measured at several locations on each sample in order to establish the statistical variations of the structural parameters within a single sample and among different samples. This work demonstrates that a detailed structural analysis of the myelin sheath can also be carried out in randomly oriented samples of intact human white matter, which is of importance for studying the aetiology and evolution of the central nervous system pathologies inducing myelin degeneration. PMID:18812651

  13. Peripheral nerve sheath tumor in a subadult golden eagle (Aquila chrysaetos).

    PubMed

    Wernick, Morena Bernadette; Dennler, Matthias; Beckmann, Kathrin; Schybli, Martina; Albini, Sarah; Hoop, Richard K; Steffen, Frank; Kircher, Patrick; Hatt, Jean-Michel

    2014-03-01

    A 5-year-old, female golden eagle (Aquila chrysaetos) was admitted with tetraplegia that progressed to a nonambulatory, spastic tetraparesis after a few days of treatment. Clinical and radiologic examinations, including radiography, computed tomography scan, and myelography, were indicative of neoplasia involving a spinal nerve root. Postmortem magnetic resonance imaging and necropsy findings confirmed the diagnosis of a peripheral nerve sheath neoplasia, not, to our knowledge, previously reported in a raptor. PMID:24881155

  14. Structural characterization of the human cerebral myelin sheath by small angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    DeFelici, M.; Felici, R.; Ferrero, C.; Tartari, A.; Gambaccini, M.; Finet, S.

    2008-10-01

    Myelin is a multi-lamellar membrane surrounding neuronal axons and increasing their conduction velocity. When investigated by small-angle x-ray scattering (SAXS), the lamellar quasi-periodical arrangement of the myelin sheath gives rise to distinct peaks, which allow the determination of its molecular organization and the dimensions of its substructures. In this study we report on the myelin sheath structural determination carried out on a set of human brain tissue samples coming from surgical biopsies of two patients: a man around 60 and a woman nearly 90 years old. The samples were extracted either from white or grey cerebral matter and did not undergo any manipulation or chemical-physical treatment, which could possibly have altered their structure, except dipping them into a formalin solution for their conservation. Analysis of the scattered intensity from white matter of intact human cerebral tissue allowed the evaluation not only of the myelin sheath periodicity but also of its electronic charge density profile. In particular, the thicknesses of the cytoplasm and extracellular regions were established, as well as those of the hydrophilic polar heads and hydrophobic tails of the lipid bilayer. SAXS patterns were measured at several locations on each sample in order to establish the statistical variations of the structural parameters within a single sample and among different samples. This work demonstrates that a detailed structural analysis of the myelin sheath can also be carried out in randomly oriented samples of intact human white matter, which is of importance for studying the aetiology and evolution of the central nervous system pathologies inducing myelin degeneration.

  15. Including sheath effects in the interpretation of planar retarding potential analyzer's low-energy ion data.

    PubMed

    Fisher, L E; Lynch, K A; Fernandes, P A; Bekkeng, T A; Moen, J; Zettergren, M; Miceli, R J; Powell, S; Lessard, M R; Horak, P

    2016-04-01

    The interpretation of planar retarding potential analyzers (RPA) during ionospheric sounding rocket missions requires modeling the thick 3D plasma sheath. This paper overviews the theory of RPAs with an emphasis placed on the impact of the sheath on current-voltage (I-V) curves. It then describes the Petite Ion Probe (PIP) which has been designed to function in this difficult regime. The data analysis procedure for this instrument is discussed in detail. Data analysis begins by modeling the sheath with the Spacecraft Plasma Interaction System (SPIS), a particle-in-cell code. Test particles are traced through the sheath and detector to determine the detector's response. A training set is constructed from these simulated curves for a support vector regression analysis which relates the properties of the I-V curve to the properties of the plasma. The first in situ use of the PIPs occurred during the MICA sounding rocket mission which launched from Poker Flat, Alaska in February of 2012. These data are presented as a case study, providing valuable cross-instrument comparisons. A heritage top-hat thermal ion electrostatic analyzer, called the HT, and a multi-needle Langmuir probe have been used to validate both the PIPs and the data analysis method. Compared to the HT, the PIP ion temperature measurements agree with a root-mean-square error of 0.023 eV. These two instruments agree on the parallel-to-B plasma flow velocity with a root-mean-square error of 130 m/s. The PIP with its field of view aligned perpendicular-to-B provided a density measurement with an 11% error compared to the multi-needle Langmuir Probe. Higher error in the other PIP's density measurement is likely due to simplifications in the SPIS model geometry.

  16. The effect of a dust size distribution on electrostatic sheaths in unmagnetized dusty plasmas

    SciTech Connect

    Benlemdjaldi, D.; Tahraoui, A.; Hugon, R.; Bougdira, J.

    2013-04-15

    In this work, the structure of plasma sheaths in presence of dust particles with different sizes is investigated numerically in a multifluid framework, where the dust size distribution is modeled by Gauss' law. For this, we have established a 1D, stationary, unmagnetized, and weakly collisional electronegative dusty plasma sheath model. The electrons and negative ions are considered in a local thermodynamic equilibrium, therefore, described by a Boltzmann distribution. On the other hand, positive ions and dust grains are described by fluid equations. The charging process is described by the orbit motion limited model. It is shown that taking into account dust grains with different sizes reduces considerably the sheath thickness. The behavior of dust surface potential is not affected, but the dust charge number is reduced, as well as the electrostatic force. It results in a decrease of layered structure. The presence of negative ions makes the structure of the electrostatic potential more oscillatory. The other physical parameters are also analyzed and discussed.

  17. Multi-Layer Electrospun Membrane Mimicking Tendon Sheath for Prevention of Tendon Adhesions

    PubMed Central

    Jiang, Shichao; Yan, Hede; Fan, Dapeng; Song, Jialin; Fan, Cunyi

    2015-01-01

    Defect of the tendon sheath after tendon injury is a main reason for tendon adhesions, but it is a daunting challenge for the biomimetic substitute of the tendon sheath after injury due to its multi-layer membrane-like structure and complex biologic functions. In this study, a multi-layer membrane with celecoxib-loaded poly(l-lactic acid)-polyethylene glycol (PELA) electrospun fibrous membrane as the outer layer, hyaluronic acid (HA) gel as middle layer, and PELA electrospun fibrous membrane as the inner layer was designed. The anti-adhesion efficacy of this multi-layer membrane was compared with a single-layer use in rabbit flexor digitorum profundus tendon model. The surface morphology showed that both PELA fibers and celecoxib-loaded PELA fibers in multi-layer membrane were uniform in size, randomly arrayed, very porous, and smooth without beads. Multi-layer membrane group had fewer peritendinous adhesions and better gliding than the PELA membrane group and control group in gross and histological observation. The similar mechanical characteristic and collagen expression of tendon repair site in the three groups indicated that the multi-layer membrane did not impair tendon healing. Taken together, our results demonstrated that such a biomimetic multi-layer sheath could be used as a potential strategy in clinics for promoting tendon gliding and preventing adhesion without poor tendon healing. PMID:25822877

  18. Ion sheath effects on RF plasma probes - Experimental results in laboratory plasmas

    NASA Technical Reports Server (NTRS)

    Kist, R.

    1977-01-01

    Laboratory work dealing with the frequency characteristic of the plasma impedance of spherical and cylindrical electrode systems is reported. The influence of the ion sheath on various features of the impedance characteristic is emphasized. Those features are the series and parallel resonance as well as additional resonances due to the excitation of electroacoustic and cyclotron harmonic waves. The dependence of the series and parallel resonances on dc biasing leads to a method of determining the ion sheath capacity for a cylindrical electrode system. The obtained values agree fairly well with those obtained from a theoretical model for the density and potential distribution in the sheath of a cylindrical sensor aligned with a supersonic plasma flow. The amplitude of resonances due to excitation of longitudinal plasma waves (electroacoustic and cyclotron harmonic) is reduced or even vanishes for sufficiently negative dc bias. Positive bias first leads to an increased amplitude up to a certain dc bias value above which, however, the amplitude decreases again due to electron absorption at the sensor surface.

  19. Investigation of particle lateral migration in sample-sheath flow of viscoelastic fluid and Newtonian fluid.

    PubMed

    Yuan, Dan; Zhang, Jun; Yan, Sheng; Peng, Gangrou; Zhao, Qianbin; Alici, Gursel; Du, Hejun; Li, Weihua

    2016-08-01

    In this work, particle lateral migration in sample-sheath flow of viscoelastic fluid and Newtonian fluid was experimentally investigated. The 4.8-μm micro-particles were dispersed in a polyethylene oxide (PEO) viscoelastic solution, and then the solution was injected into a straight rectangular channel with a deionised (DI) water Newtonian sheath flow. Micro-particles suspended in PEO solution migrated laterally to a DI water stream, but migration in the opposite direction from a DI water stream to a PEO solution stream or from one DI water stream to another DI water stream could not be achieved. The lateral migration of particles depends on the viscoelastic properties of the sample fluids. Furthermore, the effects of channel length, flow rate, and PEO concentration were studied. By using viscoelastic sample flow and Newtonian sheath flow, a selective particle lateral migration can be achieved in a simple straight channel, without any external force fields. This particle lateral migration technique could be potentially used in solution exchange fields such as automated cell staining and washing in microfluidic platforms, and holds numerous biomedical applications. PMID:27140330

  20. Morphometric analysis of connective tissue sheaths of sural nerve in diabetic and nondiabetic patients.

    PubMed

    Kundalić, Braca; Ugrenović, Slađana; Jovanović, Ivan; Stefanović, Natalija; Petrović, Vladimir; Kundalić, Jasen; Stojanović, Vesna; Živković, Vladimir; Antić, Vladimir

    2014-01-01

    One of the most common complications of diabetes mellitus is diabetic neuropathy. It may be provoked by metabolic and/or vascular factors, and depending on duration of disease, various layers of nerve may be affected. Our aim was to investigate influence of diabetes on the epineurial, perineurial, and endoneurial connective tissue sheaths. The study included 15 samples of sural nerve divided into three groups: diabetic group, peripheral vascular disease group, and control group. After morphological analysis, morphometric parameters were determined for each case using ImageJ software. Compared to the control group, the diabetic cases had significantly higher perineurial index (P < 0.05) and endoneurial connective tissue percentage (P < 0.01). The diabetic group showed significantly higher epineurial area (P < 0.01), as well as percentage of endoneurial connective tissue (P < 0.01), in relation to the peripheral vascular disease group. It is obvious that hyperglycemia and ischemia present in diabetes lead to substantial changes in connective tissue sheaths of nerve, particularly in peri- and endoneurium. Perineurial thickening and significant endoneurial fibrosis may impair the balance of endoneurial homeostasis and regenerative ability of the nerve fibers. Future investigations should focus on studying the components of extracellular matrix of connective tissue sheaths in diabetic nerves.

  1. Electrospun Polymeric Core-sheath Yarns as Drug Eluting Surgical Sutures.

    PubMed

    Padmakumar, Smrithi; Joseph, John; Neppalli, Madhuri Harsha; Mathew, Sumi Elizabeth; Nair, Shantikumar V; Shankarappa, Sahadev A; Menon, Deepthy

    2016-03-23

    Drug-coated sutures are widely used as delivery depots for antibiotics and anti-inflammatory drugs at surgical wound sites. Although drug-laden coating provides good localized drug concentration, variable loading efficiency and release kinetics limits its use. Alternatively, drug incorporation within suture matrices is hampered by the harsh fabrication conditions required for suture-strength enhancement. To circumvent these limitations, we fabricated mechanically robust electrospun core-sheath yarns as sutures, with a central poly-l-lactic acid core, and a drug-eluting poly-lactic-co-glycolic acid sheath. The electrospun sheath was incorporated with aceclofenac or insulin to demonstrate versatility of the suture in loading both chemical and biological class of drugs. Aceclofenac and insulin incorporated sutures exhibited 15% and 4% loading, and release for 10 and 7 days, respectively. Aceclofenac sutures demonstrated reduced epidermal hyperplasia and cellularity in skin-inflammation animal model, while insulin loaded sutures showed enhanced cellular migration in wound healing assay. In conclusion, we demonstrate an innovative strategy of producing mechanically strong, prolonged drug-release sutures loaded with different classes of drugs. PMID:26936629

  2. Salvianolic acid B protects the myelin sheath around injured spinal cord axons

    PubMed Central

    Zhu, Zhe; Ding, Lu; Qiu, Wen-feng; Wu, Hong-fu; Li, Rui

    2016-01-01

    Salvianolic acid B, an active pharmaceutical compound present in Salvia miltiorrhiza, exerts a neuroprotective effect in animal models of brain and spinal cord injury. Salvianolic acid B can promote recovery of neurological function; however, its protective effect on the myelin sheath after spinal cord injury remains poorly understood. Thus, in this study, in vitro tests showed that salvianolic acid B contributed to oligodendrocyte precursor cell differentiation, and the most effective dose was 20 μg/mL. For in vivo investigation, rats with spinal cord injury were intraperitoneally injected with 20 mg/kg salvianolic acid B for 8 weeks. The amount of myelin sheath and the number of regenerating axons increased, neurological function recovered, and caspase-3 expression was decreased in the spinal cord of salvianolic acid B-treated animals compared with untreated control rats. These results indicate that salvianolic acid B can protect axons and the myelin sheath, and can promote the recovery of neurological function. Its mechanism of action is likely to be associated with inhibiting apoptosis and promoting the differentiation and maturation of oligodendrocyte precursor cells. PMID:27127491

  3. Improved fluorescence properties of core-sheath electrospun nanofibers sensitized by silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Wen, Shipeng; Zhang, Rong; Hu, Shui; Zhang, Liqun; Liu, Li

    2015-09-01

    Silver nanoparticles (Ag-NPs) were used to enhance the fluorescence properties of nanofibers containing the Tb(acac)3phen (Tb = terbium, acac = acetylacetone, phen = 1,10-phenanthroline) complex. Tb(acac)3phen/PLLA//Ag-NPs/PVP (PLLA = polylacticacid, PVP = polyvinylpyrrolidone) core-sheath fluorescence nanofibers were prepared by coaxial electrospinning. SEM images demonstrated that the fibers had an average diameter of 550 nm. TEM images illustrated that the Ag-NPs and Tb(acac)3phen were uniformly dispersed in the outer and inner fibrous layers in the form of nanoparticles and molecular clusters, respectively. The fluorescence intensity of the Tb(acac)3phen/PLLA//Ag-NPs/PVP core-sheath nanofibers with a molar ratio Ag/Tb of 1 increased by 69%, the quantum efficiency increased by 53%, and the fluorescence lifetime increased by 4% over those of the fibers without Ag-NPs because of the localized surface plasmon resonance (LSPR) effect of Ag-NPs. The prepared fibers with a core-sheath structure have great potential in a wide range of fluorescence applications.

  4. Morphometric analysis of connective tissue sheaths of sural nerve in diabetic and nondiabetic patients.

    PubMed

    Kundalić, Braca; Ugrenović, Slađana; Jovanović, Ivan; Stefanović, Natalija; Petrović, Vladimir; Kundalić, Jasen; Stojanović, Vesna; Živković, Vladimir; Antić, Vladimir

    2014-01-01

    One of the most common complications of diabetes mellitus is diabetic neuropathy. It may be provoked by metabolic and/or vascular factors, and depending on duration of disease, various layers of nerve may be affected. Our aim was to investigate influence of diabetes on the epineurial, perineurial, and endoneurial connective tissue sheaths. The study included 15 samples of sural nerve divided into three groups: diabetic group, peripheral vascular disease group, and control group. After morphological analysis, morphometric parameters were determined for each case using ImageJ software. Compared to the control group, the diabetic cases had significantly higher perineurial index (P < 0.05) and endoneurial connective tissue percentage (P < 0.01). The diabetic group showed significantly higher epineurial area (P < 0.01), as well as percentage of endoneurial connective tissue (P < 0.01), in relation to the peripheral vascular disease group. It is obvious that hyperglycemia and ischemia present in diabetes lead to substantial changes in connective tissue sheaths of nerve, particularly in peri- and endoneurium. Perineurial thickening and significant endoneurial fibrosis may impair the balance of endoneurial homeostasis and regenerative ability of the nerve fibers. Future investigations should focus on studying the components of extracellular matrix of connective tissue sheaths in diabetic nerves. PMID:25147820

  5. Particle-in-cell study of the ion-to-electron sheath transition

    DOE PAGES

    Scheiner, Brett; Baalrud, Scott D.; Hopkins, Matthew M.; Yee, Benjamin T.; Barnat, Edward V.

    2016-08-09

    The form of a sheath near a small electrode, with bias changing from below to above the plasma potential, is studied using 2D particle-in-cell simulations. When the electrode is biased within Te/2e below the plasma potential, the electron velocity distribution functions (EVDFs) exhibit a loss-cone type truncation due to fast electrons overcoming the small potential difference between the electrode and plasma. No sheath is present in this regime, and the plasma remains quasineutral up to the electrode. The EVDF truncation leads to a presheath-like density and flow velocity gradients. Once the bias exceeds the plasma potential, an electron sheath ismore » present. In this case, the truncation driven behavior persists, but is accompanied by a shift in the maximum value of the EVDF that is not present in the negative bias cases. In conclusion, the flow moment has significant contributions from both the flow shift of the EVDF maximum, and the loss-cone truncation.« less

  6. High reliability sheathed, beryllia insulated, tungsten-rhenium alloy thermocouple assemblies; their fabrication and EMF stability

    NASA Technical Reports Server (NTRS)

    Burns, G. W.; Hurst, W. S.; Scroger, M. G.

    1974-01-01

    Tantalum sheathed, BeO insulated, W-3% Re/W-25% Re thermocouple assemblies were fabricated and their emf drift determined during 2059 hours of exposure at 2073 K in a gaseous helium environment. The sheathed thermocouple assemblies were constructed from aged thermoelements, specially heat-treated BeO insulators, and specially cleaned and etched tantalum sheaths. Their thermal emf drifts ranged from the equivalent of only -0.3 to -0.8 K drift per 1000 hours of exposure at 2073 K. No evidence of any gross chemical attack or degradation of the component materials was found. The emf drift and material behavior of some unsheathed, BeO insulated, W-3% Re/W-25% Re thermocouples at 2250 and 2400 K were also determined. Unsheathed thermocouples tested in an argon environment at 2250 K for 1100 hours and at 2400 K for 307 hours exhibited changes in thermal emf that typically ranged from the equivalent of a few degrees K to as much as +11 K. Post-test examinations of these thermocouples revealed some undesirable material degradation and interaction which included erosion of the BeO insulators and contamination of the thermoelements by tantalum from the tantalum blackbody enclosure in which the thermocouples were contained.

  7. Low thermal conductive Bi-2223 tapes sheathed with Ag-Au alloys

    SciTech Connect

    Fujishiro, Hiroyuki; Ikebe, Manabu; Noto, Koshichi; Matsukawa, Michiaki,; Sasaoka, Takaaki; Nomura, Katsumi; Sato, Junichi; Kuma, Shoji,

    1994-07-01

    With the view of applying to power current leads for superconducting magnet systems and for other cryogenic power handling systems, low thermal conductive Bi-2223 superconducting tapes sheathed with Ag-Au alloy were measured from 12 to 260K. The critical current density (overall-J) was about 1,700A/cm{sup 2} at 77K, 0T and remained nearly constant irrespective of Au concentration up to 11 at %. The tape sheathed with Ag + 11at.% Au alloy, of which the superconductor cross-section ratio f{sub sc} was 0.65, had a thermal conductivity value about 0.2W/cmK at 77K. This value is as low as that of Cu-Zu. It was found that the thermal conductivity of the tape was close to the calculated one based on f{sub sc} and the independently measured thermal conductivities of the Ag-Au alloy and the Bi-2223 superconductor. The superconducting tapes sheathed with the alloy were confirmed to be suitable for the application as power current leads.

  8. Acute optic nerve sheath fenestration in humans using the free electron laser (FEL): a case report

    NASA Astrophysics Data System (ADS)

    Joos, Karen M.; Mawn, Louise A.; Shen, Jin-Hui; Jansen, E. Duco; Casagrande, Vivien A.

    2002-06-01

    Our previous studies using rabbits and monkeys showed that the Amide II wavelength (6.45 micrometers ) produced by the FEL could efficiently produce an optic nerve sheath fenestration with minimal damage. In order to determine if the technology safely could be applied to human surgery, we used 2 blind human eyes during enucleation to compare the results of producing fenestrations with the FEL or a scissors. FDA and Vanderbilt IRB approvals, and individual patient consents were obtained. The FEL energy was transmitted to a human operating room. After disinsertion of the medial rectus muscle, an optic nerve sheath fenestration (2 mm diameter) was made with either the FEL (6.45 micrometers , 325 micrometers spot size, 30 Hz, 3 mJ) through a hollow waveguide surgical probe or with a scissors. The enucleation was then completed. The optic nerve was dissected from the globe and fixed. Specimens were examined histologically. Dural incisions were effective with both methods. FEL energy at 6.45 micrometers can be transmitted to an operating room and delivered to human ocular tissue through a hollow waveguide surgical probe. This FEL wavelength can produce an optic nerve sheath fenestration without acute direct damage to the nerve in this case report.

  9. Adaptation strategies of the sheathed cyanobacterium Lyngbya majuscula to ultraviolet-B.

    PubMed

    Mandal, Sikha; Rath, Jnanendra; Adhikary, Siba Prasad

    2011-02-01

    Lyngbya majuscula is a dominant organism in the east coast of India forming characteristic mat in dried saline soils simultaneously exposed to solar radiation of the tropics. Studies on the growth response, changes in the spectral properties of the methanolic extract and protein profile of this estuarine sheathed cyanobacterium to UV-B revealed existence of effective adaptation mechanism to withstand prolonged UV-B radiation. Carotenoids along with MAAs of the organism was increased with increase in UV irradiation. Increase in thickness of the mucilaginous sheath layer as well as cellular carbohydrate content was observed upon exposure to prolonged UV-B dose. Induction of 21 and 33 kDa low molecular weight proteins, and a 99 kDa protein together with formation of distinct multilayered sheath embedding trichomes with granulated cells were the adaptive features of the organism to cope with UV-B stress. The organism was considerably revived after incubating the irradiated cells in mineral medium under florescent light and in the dark suggesting existence of photoreactivation and dark repair in this cyanobacterium. However more experiments are needed to establish the existence of photoreactivation and dark repair mechanism in the studied cyanobacterium.

  10. Influences of Turbulent Reentry Plasma Sheath on Wave Scattering and Propagation

    NASA Astrophysics Data System (ADS)

    Liu, Zhiwei; Bao, Weimin; Li, Xiaoping; Shi, Lei; Liu, Donglin

    2016-06-01

    The randomness of turbulent reentry plasma sheaths can affect the propagation and scattering properties of electromagnetic waves. This paper developed algorithms to estimate the influences. With the algorithms and typical reentry data, influences of GPS frequency and Ka frequency are studied respectively. Results show that, in terms of wave scattering, the scattering loss caused by the randomness of the turbulent plasma sheath increases with the increase of the ensemble average electron density, ensemble average collision frequency, electron density fluctuation and turbulence integral scale respectively. Also the scattering loss is much smaller than the dielectric loss. The scattering loss of Ka frequency is much less than that of the GPS frequency. In terms of wave propagation, the randomness arouses the fluctuations of amplitude and phase of waves. The fluctuations change with altitudes that when the altitude is below 30 km, fluctuations increase with altitude increasing, and when the altitude is above 30 km, fluctuations decrease with altitude increasing. The fluctuations of GPS frequency are strong enough to affect the tracking, telemetry, and command at appropriate conditions, while the fluctuations of Ka frequency are much more feeble. This suggests that the Ka frequency suffers less influences of the randomness of a turbulent plasma sheath. supported by the National Basic Research Program of China (No. 2014CB340205) and National Natural Science Foundation of China (Nos. 61301173 and 61473228)

  11. A new TGF-β3 controlled-released chitosan scaffold for tissue engineering synovial sheath.

    PubMed

    Jiang, Ke; Wang, Ziming; Du, Quanyin; Yu, Jiang; Wang, Aimin; Xiong, Yan

    2014-03-01

    The post-operative outcome of flexor tendon healing remains limited by flexor tendon adhesion that reduces joint range of motion. Despite improvement in different methods, peritendinous adhesion formation continues to present a formidable challenge. Recent studies showed that transforming growth factor-β3 (TGF-β3) may be the key factor to reducing adhesion formation in skin or tendon. In this study, we designed a novel type of tissue engineering synovial sheath containing TGF-β3, to prevent flexor tendon adhesion. First, to achieve a stable release of TGF-β3, chitosan microspheres, prepared by crosslinking-emulsion, were used for the delivery of TGF-β3. Second, a three-dimensional chitosan scaffold was prepared by lyophilization, and TGF-β3 microspheres were carefully introduced into the scaffold. Then, synovial cells were cultured and then seeded into the TGF-β3 loaded scaffold to produce TGF-β3 controlled-released tissue engineering synovial sheath. Tests clearly demonstrated that the scaffold has good structure and compatibility with cells. These results expand the feasibility of combinative strategies of controlled protein release and tissue-engineered synovial sheath formation. Application of this scaffold to tendon repair sites may help to prevent adhesion of tendon healing.

  12. Linear electromagnetic excitation of an asymmetric low pressure capacitive discharge with unequal sheath widths

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.; Lichtenberg, A. J.; Kawamura, E.; Chabert, P.

    2016-01-01

    It is well-known that standing waves having radially center-high radio frequency (rf) voltage profiles exist in high frequency capacitive discharges. In this work, we determine the symmetric and antisymmetric radially propagating waves in a cylindrical capacitive discharge that is asymmetrically driven at the lower electrode by an rf voltage source. The discharge is modeled as a uniform bulk plasma which at lower frequencies has a thicker sheath at the smaller area powered electrode and a thinner sheath at the larger area grounded electrode. These are self-consistently determined at a specified density using the Child law to calculate sheath widths and the electron power balance to calculate the rf voltage. The fields and the system resonant frequencies are determined. The center-to-edge voltage ratio on the powered electrode is calculated versus frequency, and central highs are found near the resonances. The results are compared with simulations in a similar geometry using a two-dimensional hybrid fluid-analytical code, giving mainly a reasonable agreement. The analytic model may be useful for finding good operating frequencies for a given discharge geometry and power.

  13. Investigating the Structure of the Wake of a Dust Particle in the Plasma Sheath

    NASA Astrophysics Data System (ADS)

    Jung, Hendrik; Greiner, Franko; Piel, Alexander

    2015-11-01

    Due to the deflection of the ambient streaming ions, a negatively charged dust particle in the plasma sheath forms a wake with a net positive space charge in downstream direction. The wake is characterized by attractive, non-reciprocal forces between negatively charged particles and a charge reduction of a particle in the wake of another particle. In this contribution a two-particle system is used to investigate the ion wake structure behind a dust particle in the plasma sheath of an rf discharge. For this purpose, we have used the phase-resolved resonance method that evaluates the dynamic response of the particle system to small external, sinusoidal perturbations, which allows to measure the wake induces characteristics. Plasma inherent etching processes are used to achieve an increasing levitation height of the lower particle, so that the structure of the wake of the upper particle, which is nearly unaffected by etching, can be probed. In good agreement with theoretical predictions, a significant modification in the plasma sheath to one long potential tail is observed. The presented method is used to investigate the influence of a strong magnetic field on the formation and spatial structure of the wake. Funded by DFG under contract SFB TR-24/A2.

  14. Self-consistent modeling of the tokamak RF antennas, edge plasma, and sheath voltages

    NASA Astrophysics Data System (ADS)

    Smithe, David; Jenkins, Tom; Austin, Travis; Loverich, John; Stoltz, Peter

    2012-10-01

    We model the 24-strap ITER RF antenna with a time-domain electromagnetic simulation package [1] that faithfully represents the 3D complexity of the launcher geometry. The simulations include a cold-plasma fluid model of the edge plasma [2], with an RF sheath sub-grid model which allows for realistic behavior of plasma in contact with metallic structures, such as Faraday shields [3]. Interestingly, localized short wavelength modes, likely slow waves, have been observed in the vicinity of the launcher, and are very sensitive to density. We investigate the effect on these waves for varying density, density profile, and magnetic shear. We further investigate the contribution to high sheath potentials such waves might have. We also present status and additional highlights of the continuing evolution of the overall model. This includes studies to benchmark the nonlinear sheath width and loss parameters, and more diagnostics aimed towards better characterizing energy balance. It also includes application of the analysis on larger problem domain size, with scaling-study results. Finally, we review recent work to improve the model for warm plasma, and nonlinear effects. Work supported by US. DOE Grants DE-FG02-09ER55006 and DE-FC02-08ER54953.[4pt] [1] Nieter, C. and Cary, J. R., JCP 196 (2004) 448-473.[0pt] [2] Smithe, D., Physics of Plasmas 14, 056104 (2007).[0pt] [3] Myra and D'Ippolito, PRL 101, 195004 (2008).

  15. Acute optic nerve sheath fenestration with the free-electron laser

    NASA Astrophysics Data System (ADS)

    Shen, Jin-Hui; Casagrande, Vivien A.; Joos, Karen M.; Shetlar, Debra J.; Robinson, Richard D.; Head, William S.; Mavity-Hudson, Julia A.; Nunnally, Amy H.

    1999-06-01

    Purpose: To determine if the free electron laser (FEL) energy can be delivered to a small space to perform optic nerve sheath fenestration with minimal acute nerve damage. Methods: A 530 mm hollow waveguide probe was designed. Optic nerve sheath fenestration (1.0 mm diameter) was performed in 8 rabbits using either the FEL (4 eyes, 6.45mm, 10 Hz, 2 mJ) or a knife (4 eyes). Within 2 hours following surgery, the animals were perfused with aldehyde fixative. The integrity of the optic nerve and glial response at the site of fenestration were evaluated on tissue selections with H&E, and antibodies to S100β or GFAP. Results: Surgery using the FEL probe was found to be technically superior to the knife. The glial reaction was limited to a zone adjacent to the fenestration and was similar in both the FEL and knife incisions. Conclusions: The FEL appears capable of efficiently performing an optic nerve sheath fenestration in a small space with minimal acute damage. Both the FEL and knife incisions result in a rapid glial response at the site of fenestration even when optic nerve integrity is not compromised.

  16. Laser Microdissection of Narrow Sheath Mutant Maize Uncovers Novel Gene Expression in the Shoot Apical Meristem

    PubMed Central

    Zhang, Xiaolan; Madi, Shahinez; Borsuk, Lisa; Nettleton, Dan; Elshire, Robert J; Buckner, Brent; Janick-Buckner, Diane; Beck, Jon; Timmermans, Marja; Schnable, Patrick S; Scanlon, Michael J

    2007-01-01

    Microarrays enable comparative analyses of gene expression on a genomic scale, however these experiments frequently identify an abundance of differentially expressed genes such that it may be difficult to identify discrete functional networks that are hidden within large microarray datasets. Microarray analyses in which mutant organisms are compared to nonmutant siblings can be especially problematic when the gene of interest is expressed in relatively few cells. Here, we describe the use of laser microdissection microarray to perform transcriptional profiling of the maize shoot apical meristem (SAM), a ~100-μm pillar of organogenic cells that is required for leaf initiation. Microarray analyses compared differential gene expression within the SAM and incipient leaf primordium of nonmutant and narrow sheath mutant plants, which harbored mutations in the duplicate genes narrow sheath1 (ns1) and narrow sheath2 (ns2). Expressed in eight to ten cells within the SAM, ns1 and ns2 encode paralogous WUSCHEL1-like homeobox (WOX) transcription factors required for recruitment of leaf initials that give rise to a large lateral domain within maize leaves. The data illustrate the utility of laser microdissection-microarray analyses to identify a relatively small number of genes that are differentially expressed within the SAM. Moreover, these analyses reveal potentially conserved WOX gene functions and implicate specific hormonal and signaling pathways during early events in maize leaf development. PMID:17571927

  17. Axonal selection and myelin sheath generation in the central nervous system.

    PubMed

    Simons, Mikael; Lyons, David A

    2013-08-01

    The formation of myelin in the central nervous system is a multi-step process that involves coordinated cell-cell interactions and dramatic changes in plasma membrane architecture. First, oligodendrocytes send our numerous highly ramified processes to sample the axonal environment and decide which axon(s) to select for myelination. After this decision is made and individual axon to oligodendrocyte contact has been established, the exploratory process of the oligodendrocyte is converted into a flat sheath that spreads and winds along and around its associated axon to generate a multilayered membrane stack. By compaction of the opposing extracellular layers of membrane and extrusion of almost all cytoplasm from the intracellular domain of the sheath, the characteristic membrane-rich multi-lamellar structure of myelin is formed. Here we highlight recent advances in identifying biophysical and signalling based mechanisms that are involved in axonal selection and myelin sheath generation by oligodendrocytes. A thorough understanding of the mechanisms underlying these events is a prerequisite for the design of novel myelin repair strategies in demyelinating and dysmyelinating diseases.

  18. Identification of QTLs and possible candidate genes conferring sheath blight resistance in rice (Oryza sativa L.).

    PubMed

    Yadav, Shailesh; Anuradha, Ghanta; Kumar, Ravi Ranjan; Vemireddy, Lakshminaryana Reddy; Sudhakar, Ravuru; Donempudi, Krishnaveni; Venkata, Durgarani; Jabeen, Farzana; Narasimhan, Yamini Kalinati; Marathi, Balram; Siddiq, Ebrahimali Abubacker

    2015-01-01

    Sheath blight, caused by the pathogenic fungus Rhizoctonia solani Kühn, is one of the most devastating diseases in rice. Breeders have always faced challenges in acquiring reliable and absolute resistance to this disease in existing rice germplasm. In this context, 40 rice germplasm including eight wild, four landraces, twenty- six cultivated and two advanced breeding lines were screened utilizing the colonized bits of typha. Except Tetep and ARC10531 which expressed moderate level of resistance to the disease, none could be found to be authentically resistant. In order to map the quantitative trait loci (QTLs) governing the sheath blight resistance, two mapping populations (F2 and BC1F2) were developed from the cross BPT-5204/ARC10531. Utilizing composite interval mapping analysis, 9 QTLs mapped to five different chromosomes were identified with phenotypic variance ranging from 8.40 to 21.76%. Two SSR markers namely RM336 and RM205 were found to be closely associated with the major QTLs qshb7.3 and qshb9.2 respectively and were attested as well in BC1F2 population by bulk segregant analysis approach. A hypothetical β 1-3 glucanase with other 31 candidate genes were identified in silico utilizing rice database RAP-DB within the identified QTL region qshb9.2. A detailed insight into these candidate genes will facilitate at molecular level the intricate nature of sheath blight, a step forward towards functional genomics.

  19. Association between QTLs and morphological traits toward sheath blight resistance in rice (Oryza sativa L.)

    PubMed Central

    Hossain, Md Kamal; Jena, Kshirod Kumar; Bhuiyan, Md Atiqur Rahman; Wickneswari, Ratnam

    2016-01-01

    Sheath blight is considered the most significant disease of rice and causes enormous yield losses over the world. Breeding for resistant varieties is the only viable option to combat the disease efficiently. Seventeen diverged rice genotypes along with 17 QTL-linked SSR markers were evaluated under greenhouse conditions. Pearson’s correlation showed only the flag leaf angle had a significant correlation with sheath blight resistance under greenhouse screening. Multivariate analysis based on UPGMA clustering and principal component analysis (PCA) indicated that the flag leaf angle, flag leaf length, and plant compactness were significantly associated with the following SSR marker alleles: RM209 (116,130), RM202 (176), RM224 (126), RM257 (156), RM426 (175), and RM6971 (196), which are linked to the SB QTLs: QRlh11, qSBR11-3, qSBR11-1, qSBR9-1, qShB3-2, and qSB-9. A Mantel test suggested a weak relationship between the observed phenotypes and allelic variation patterns, implying the independent nature of morphological and molecular variations. Teqing and Tetep were found to be the most resistant cultivars. IR65482-4-136-2-2, MR219-4, and MR264 showed improved resistance potentials. These results suggest that the morphological traits and QTLs which have been found to associate with sheath blight resistance are a good choice to enhance resistance through pyramiding either 2 QTLs or QTLs and traits in susceptible rice cultivars. PMID:27795687

  20. Preparation and evaluation of Bacillus megaterium-alginate microcapsules for control of rice sheath blight disease.

    PubMed

    Wiwattanapatapee, R; Chumthong, A; Pengnoo, A; Kanjanamaneesathian, M

    2013-08-01

    Bacillus megaterium encapsulated in calcium alginate microcapsules was prepared and tested for its efficacy against sheath blight disease of rice. In laboratory conditions, the aqueous suspension (1:100, v/v in potato dextrose agar) of the bacterial microcapsules (10(10) spores/ml) inhibited mycelial growth of Rhizoctonia solani (>99 %) after the microcapsules were produced and stored for 12 months at room temperature (28 ± 2 °C). The survival of the bacterium in the microcapsules in response to ultraviolet (u.v.) irradiation and high temperature was investigated. The survivability of the bacterium in the encapsulated form was greater than that of the fresh cells when it was subjected to u.v. (20-W General electric u.v. lamp from a 25 cm distance for 48 h) and a high temperature treatment (80 °C for 48 h). Cells of the bacterium were detected by scanning electron microscope on both the leaf sheath and the leaf blade (in pot tests in a greenhouse) after spraying encapsulated product. The number of bacteria on the surface of both rice tissues (5 Log. number/g of plant) after spraying with encapsulated product was not significantly different from that after spraying with fresh cells onto the rice seedlings. Spraying the encapsulated B. megaterium on rice plants in the greenhouse was as effective as spraying a chemical fungicide for suppressing rice sheath blight disease.

  1. Morphometric Analysis of Connective Tissue Sheaths of Sural Nerve in Diabetic and Nondiabetic Patients

    PubMed Central

    Kundalić, Braca; Ugrenović, Slađana; Jovanović, Ivan; Stefanović, Natalija; Petrović, Vladimir; Kundalić, Jasen; Stojanović, Vesna; Živković, Vladimir; Antić, Vladimir

    2014-01-01

    One of the most common complications of diabetes mellitus is diabetic neuropathy. It may be provoked by metabolic and/or vascular factors, and depending on duration of disease, various layers of nerve may be affected. Our aim was to investigate influence of diabetes on the epineurial, perineurial, and endoneurial connective tissue sheaths. The study included 15 samples of sural nerve divided into three groups: diabetic group, peripheral vascular disease group, and control group. After morphological analysis, morphometric parameters were determined for each case using ImageJ software. Compared to the control group, the diabetic cases had significantly higher perineurial index (P < 0.05) and endoneurial connective tissue percentage (P < 0.01). The diabetic group showed significantly higher epineurial area (P < 0.01), as well as percentage of endoneurial connective tissue (P < 0.01), in relation to the peripheral vascular disease group. It is obvious that hyperglycemia and ischemia present in diabetes lead to substantial changes in connective tissue sheaths of nerve, particularly in peri- and endoneurium. Perineurial thickening and significant endoneurial fibrosis may impair the balance of endoneurial homeostasis and regenerative ability of the nerve fibers. Future investigations should focus on studying the components of extracellular matrix of connective tissue sheaths in diabetic nerves. PMID:25147820

  2. Fast equilibrium micro-extraction from biological fluids with biocompatible core-sheath electrospun nanofibers.

    PubMed

    Wu, Qian; Wu, Dapeng; Guan, Yafeng

    2013-06-18

    Sample preparation methods with high temporal resolution and matrix resistance will benefit fast direct analysis of analytes in a complex matrix, such as drug monitoring in biofluids. In this work, the core-sheath biocompatible electrospun nanofiber was fabricated as a micro-solid phase extraction material. With the poly(N-isopropylacrylamide) (PNIPAAm) as sheath polymer and polystyrene (PS) as core polymer, the fiber membrane was highly hydrophilic and exhibited good antifouling ability to proteins and cells. Its complete expansion in aqueous solution and its nanoscale fiber (100-200 nm) structure offered high mass transfer rate of analytes between liquid and solid phases. The equilibration time of microextraction with this membrane was all shorter than 2 min for eight drugs tested, and the linear ranges covered more than 3 orders of magnitude for most of them. This membrane could be applied to monitor free drugs in plasma and their protein binding kinetics by equilibrium-microextraction with a 2 min temporal resolution. The results showed that the core-sheath electrospun nanofiber membrane would be a better alternative of solid phase material for microextraction with good matrix-resistance ability and high temporal resolution. PMID:23700975

  3. Use of Silica Sol Step Gradients to Prepare Bundle Sheath and Mesophyll Chloroplasts from Panicum maximum.

    PubMed

    Walbot, V

    1977-07-01

    The first method for the direct separation of mesophyll and bundle sheath chloroplasts from whole tissue homogenates of a C(4) plant is described. Centrifugation of mixed chloroplast preparations from Panicum maximum through low viscosity silica sol gradients effectively separates large, starch-containing chloroplasts from smaller plastids. The large chloroplasts are judged to be bundle sheath chloroplasts on the basis of microscopic appearance, the presence of starch grains, the protein complement displayed on sodium dodecyl sulfate acrylamide gels, and the exclusive localization of ribulose bisphosphate carboxylase activity in these plastids. As a measure of intactness both the large (bundle sheath) and small (mesophyll) chloroplasts contain glyceralde-hyde-3-phosphate NADP-dependent dehydrogenase activity that is greatly enhanced by plastid lysis and both chloroplast preparations are impermeable to deoxyribonuclease. Chloroplast enzyme activities are inhibited by silica sol due to the Mg(2+) chelating activity of this reagent. However, well washed chloroplasts separated on silica gradients had enzyme activities similar to reported values in which silica sol gradients were not used. PMID:16660019

  4. Radio-frequency sheaths physics: Experimental characterization on Tore Supra and related self-consistent modeling

    SciTech Connect

    Jacquot, Jonathan; Colas, Laurent Corre, Yann; Goniche, Marc; Gunn, Jamie; Kubič, Martin; Milanesio, Daniele; Heuraux, Stéphane

    2014-06-15

    During the 2011 experimental campaign, one of the three ion cyclotron resonance heating (ICRH) antennas in the Tore Supra tokamak was equipped with a new type of Faraday screen (FS). The new design aimed at minimizing the integrated parallel electric field over long field lines as well as increasing the heat exhaust capability of the actively cooled screen. It proved to be inefficient for attenuating the radio-frequency (RF)-sheaths on the screen itself on the contrary to the heat exhaust concept that allowed operation despite higher heat fluxes on the antenna. In parallel, a new approach has been proposed to model self-consistently RF sheaths: the SSWICH (Self-consistent Sheaths and Waves for IC Heating) code. Simulations results from SSWICH coupled with the TOPICA antenna code were able to reproduce the difference between the two FS designs and part of the spatial pattern of heat loads and Langmuir probe floating potential. The poloidal pattern is a reliable result that mainly depends on the electrical design of the antenna while the radial pattern is on the contrary highly sensitive to loosely constrained parameters such as perpendicular conductivity that generates a DC current circulation from the private region inside the antenna limiters to the free scrape off layer outside these limiters. Moreover, the cantilevered bars seem to be the element in the screen design that enhanced the plasma potential.

  5. Tolerance of the carotid-sheath contents to brachytherapy: an experimental study

    SciTech Connect

    Werber, J.L.; Sood, B.; Alfieri, A.; McCormick, S.A.; Vikram, B. )

    1991-06-01

    Tumor invasion of the carotid artery is a potential indication for brachytherapy, which delivers a high dose of irradiation to residual tumor while limiting the dose to adjacent healthy tissues. The tolerance of carotid-sheath contents to varying doses of brachytherapy, however, has not been clearly established. In order to evaluate brachytherapy effects on carotid-sheath contents, after-loading catheters were implanted bilaterally in 3 groups of 6 rabbits each (18 rabbits). Iridium 192 brachytherapy doses of either 5000 cGy (rad), 9000 cGy, or 13,000 cGy were delivered unilaterally, with the contralateral neck serving as a nonirradiated control in each animal. There were no carotid ruptures and wound healing was normal. Two animals from each group were killed at 6, 20, and 48 weeks. Even at the highest dose (13,000 cGy), nerve conduction studies performed on the vagus nerve prior to sacrifice revealed no increased latency, histologic changes were minimal, and carotid arteries were patent. These observations suggest that the carotid-sheath contents in healthy rabbits could tolerate high doses (up to 13,000 cGy) of low-dose-rate interstitial brachytherapy without complications.

  6. Contact Force-Guided Deep Engagement with a Steerable Sheath in the Distal Great Cardiac Vein: A Case Report.

    PubMed

    Kumagai, Y U; Arimoto, Takanori; Iwayama, Tadateru; Hashimoto, Naoaki; Watanabe, Tetsu; Kubota, Isao

    2016-05-01

    Ablation of ventricular tachycardia originating from the great cardiac vein involves the difficult step of deep engagement with an ablation catheter. The catheter and a steerable sheath (MobiCath, Biosense Webster, Diamond Bar, CA, USA) were advanced alternately only when the contact force vector was parallel to the coronary venous system. Deep engagement with a steerable sheath ensured a powerful backup force during ablation. PMID:26854279

  7. Numerical solutions of sheath structures in front of an electron-emitting electrode immersed in a low-density plasma

    SciTech Connect

    Din, Alif

    2013-09-15

    The exact theoretical expressions involved in the formation of sheath in front of an electron emitting electrode immersed in a low-density plasma have been derived. The potential profile in the sheath region has been calculated for subcritical, critical, and supercritical emissions. The potential profiles of critical and supercritical emissions reveals that we must take into account a small, instead of zero, electric field at the sheath edge to satisfy the boundary conditions used to integrate the Poisson's equation. The I-V curves for critical emission shows that only high values of plasma-electron to emitted-electron temperature ratio can meet the floating potential of the emissive electrode. A one-dimensional fluid like model is assumed for ions, while the electron species are treated as kinetic. The distribution of emitted-electron from the electrode is assumed to be half Maxwellian. The plasma-electron enters the sheath region at sheath edge with half Maxwellian velocity distribution, while the reflected ones have cut-off velocity distribution due to the absorption of super thermal electrons by the electrode. The effect of varying emitted-electron current on the sheath structure has been studied with the help of a parameter G (the ratio of emitted-electron to plasma-electron densities)

  8. Reduced turnover times make flexible optical reusable scope with EndoSheath(®) Technology significantly cost-effective.

    PubMed

    Gupta, Deepak; Srirajakalidindi, Arvind; Wang, Hong

    2012-07-01

    EndoSheath bronchoscopy (Vision Sciences, Inc.) uses a sterile, disposable microbial barrier that may meet the growing needs for safe, efficient, and cost effective flexible bronchoscopy. The purpose of this open-label comparative study was to compare and calculate the costs-per-airway-procedure of the reusable fiberscope when used with and without EndoSheath(®) Technology; and to record the turnover time from the completion of the use of each scope until its readiness again for the next use. Seventy-five new patients' airways requiring airway maneuvers and manipulations with Vision Sciences, Inc., reusable fiberscope with EndoSheath(®) Technology were evaluated for the costs comparisons with reassessed historical costs data for Olympus scope assisted tracheal intubations. As compared to costs of an intubation ($158.50) with Olympus scope at our institute, the intubation costs with Vision Sciences, Inc., reusable fiberscope with EndoSheath technology was $81.50 (P < 0.001). The mean turnover time was 5.44 min with EndoSheath technology as compared to previously reported 30 min with Olympus fiberscope (P < 0.001). Based on our institutional experience, Vision Sciences, Inc., reusable fiberscope with EndoSheath technology is significantly cost effective as compared to the Olympus scope with significantly improved turnover times.

  9. Manufacture of (Bi,Pb)2Sr2Ca2Cu3O10-based tapes with a composite sheath

    NASA Astrophysics Data System (ADS)

    Grivel, J.-C.; Abrahamsen, A. B.; Andersen, N. H.; Saksl, K.

    2008-02-01

    (Bi,Pb)2Sr2Ca2Cu3O10-based single-filament tapes were prepared using a pure Ag protective sheath in contact with the ceramic core and an external sheath consisting of Ni. The influence of the composite sheath geometry on the (Bi,Pb)2Sr2Ca2Cu3O10 phase formation kinetics was studied by in-situ synchrotron x-ray diffraction in a 8.5% O2 - 91.5% N2 gas mixture and was found to depend strongly on the sheath architecture as a consequence of differences in the oxygen supply between the ceramic core and the outer atmosphere. Owing to the efficient protection of the pure Ag layer against Ni diffusion, the critical temperature of the (Bi,Pb)2Sr2Ca2Cu3O10 phase is unaffected. Critical current densities as high as 35 kA/cm2 (77K, self field) were obtained in a single heat treatment when a slow cooling rate was used. The ceramic density was significantly improved in comparison with that of tapes prepared using only pure Ag as sheath material and heat treated once. This effect can be attributed to the higher mechanical strength of the composite sheath at elevated temperatures, which prevents the development of an otherwise significant porosity during the growth of the superconducting crystallites.

  10. FAST: A Fuel And Sheath Modeling Tool for CANDU Reactor Fuel

    NASA Astrophysics Data System (ADS)

    Prudil, Andrew Albert

    Understanding the behaviour of nuclear fuel during irradiation is a complicated multiphysics problem involving neutronics, chemistry, radiation physics, material-science, solid mechanics, heat transfer and thermal-hydraulics. Due to the complexity and interdependence of the physics and models involved, fuel modeling is typically clone with numerical models. Advancements in both computer hardware and software have made possible new more complex and sophisticated fuel modeling codes. The Fuel And Sheath modelling Tool (FAST) is a fuel performance code that has been developed for modeling nuclear fuel behaviour under normal and transient conditions. The FAST code includes models for heat generation and transport, thermal expansion, elastic strain, densification, fission product swelling, pellet relocation, contact, grain growth, fission gas release, gas and coolant pressure and sheath creep. These models are coupled and solved numerically using the Comsol Multiphysics finite-element platform. The model utilizes a radialaxial geometry of a fuel pellet (including dishing and chamfering) and accompanying fuel sheath allowing the model to predict circumferential ridging. This model has evolved from previous treatments developed at the Royal Military College. The model has now been significantly advanced to include: a more detailed pellet geometry, localized pellet-to-sheath gap size and contact pressure, ability to model cracked pellets, localized fuel burnup for material property models, improved U02 densification behaviour, fully 2-dimensional model for the sheath, additional creep models, additional material models, an FEM Booth-diffusion model for fission gas release (including ability to model temperature and power changes), a capability for end-of-life predictions, the ability to utilize text files as model inputs, and provides a first time integration of normal operating conditions (NOC) and transient fuel models into a single code (which has never been achieved

  11. Radiation Emission Correlated with the Evolution of Current Sheath from a Deuterium Plasma Focus

    NASA Astrophysics Data System (ADS)

    Rafique, M. Shahid; Lee, P.; Patran, A.; Rawat, R. S.; Lee, S.

    2010-06-01

    The time resolved emission of neutrons and X-rays (both soft and hard) is correlated with the current sheath evolution during the radial phase of a 3.2 kJ Mather-type plasma focus device operated in deuterium at an optimised pressure of 4 mbar. A three-frame computer-controlled laser shadowgraphy system was incorporated in the experiment to investigate the time evolution of the radial phase of the plasma focus. The dynamics of the sheath was then correlated with the time resolved X-rays and neutron emission. The time-resolved neuron and hard X-ray emission was detected by a Scintillator-photomultiplier system while the time resolved soft X-rays were detected employing filtered PIN photo diodes. The observations were recorded with a temporal accuracy of a few ns. For the reference, the total neutron yield was also monitored by an Indium Foil activation detector. The correlation with the High Voltage Probe signal of the discharge, together with the X-ray and neutron emission regimes enabled to identify the important periods of the sheath evolution i.e. the radial compression (pre focus), minimum pinch radius (focus) and the post focus phenomena. During the initial stage of the radial phase, velocities of 10-23 cm/μs, while at the later stage of the radial phase (up till the compression), velocities up to 32-42 cm/μs were measured in our experiment. For the discharges with the lower neutron yield (lower than the average value ~1 × 108 n/discharge), the current sheath appears to be disturbed and neutron and hard X-ray signal profiles do not carry much information whereas the soft X-ray emission is significant. For the discharges with high neutron yield (higher than the average value), the current sheath has a smooth structure until the maximum compression occurs. Hard X-ray emission is maximum for the discharges with high neutron yield, especially whenever there is development of m = 0 instability compressing the column to very high densities. The neutron are

  12. T2-weighted magnetic resonance imaging measurements of optic nerve sheath diameter in dogs with and without presumed intracranial hypertension.

    PubMed

    Scrivani, Peter V; Fletcher, Daniel J; Cooley, Stacy D; Rosenblatt, Alana J; Erb, Hollis N

    2013-01-01

    Intracranial hypertension is a cause of cerebral ischemia and neurologic deficits in dogs. Goals of this retrospective study were to test interobserver agreement for MRI measurements of optic nerve sheath diameter and associations between optic nerve sheath diameter, signalment data, and presumed intracranial hypertension status in a cohort of dogs. A veterinary radiologist interpreted scans of 100 dogs and dogs were assigned to groups based on presence or absence of at least two MRI characteristics of presumed intracranial hypertension. Two observers who were unaware of group status independently measured optic nerve diameter from transverse T2-weighted sequences. Mean optic nerve sheath diameter for all dogs was 3 mm (1-4 mm). The mean difference between observers was 0.3 mm (limits of agreement, -0.4 and 1.0 mm). There was no correlation between optic nerve sheath diameter and age for either observer (r = -0.06 to 0.00) but a moderate positive correlation was observed between optic nerve sheath diameter and body weight for both observers (r = 0.70-0.76). The 22 dogs with presumed intracranial hypertension weighed less than the 78 dogs without (P = 0.02) and were more often female (P = 0.04). Dogs with presumed intracranial hypertension had a larger ratio of optic nerve sheath diameter to body weight for each observer-side pair (P = 0.01-0.04) than dogs without. Findings indicated that the ratio of MRI optic nerve sheath diameter relative to body weight may be a repeatable predictor of intracranial hypertension in dogs.

  13. Presence of N-L-lactyl-D-perosamine residue in the sheath-forming polysaccharide of Thiothrix fructosivorans.

    PubMed

    Kawasaki, Yuta; Kondo, Keiko; Narizuka, Rie; Endo, Tomoyuki; Katahira, Masato; Kawamura, Izuru; Sato, Michio; Takeda, Minoru

    2016-01-01

    Thiothrix fructosivorans forms a microtube (sheath) that encloses a line of cells. This sheath is an assemblage of [→4)-GlcN-(1→4)-Glc-(1→]n with side chains of Rha4N-(1→3)-Fuc(1→ at position 3 of Glc. The sheath-forming polysaccharide (SFP) may have some substitutions but this is not yet confirmed. To investigate the possible substitutions, the sheath was prepared by mild treatments. Solid-state NMR analysis suggested the presence of N-substitution. The sheath was hydrolyzed with concentrated HCl at 0°C, followed by derivatization with 4-aminobenzoic acid ethyl ester (ABEE). The presence of N-lactyl-Rha4N-Fuc-ABEE was suggested by NMR spectroscopy. Lactic acid was determined to be the l-isomer by chiral HPLC analysis. To estimate the N-lactylation degree, the sheath was N-acetylated. N-Acetyl-Rha4N-Fuc-ABEE and N-lactyl-Rha4N-Fuc-ABEE were then collectively recovered, and their abundance ratio was determined to be 1:4 by NMR analysis. When hydrolysis was performed at 40°C, GlcNAc-ABEE was obtained. For estimation of the N-acetylation degree, the sheath was N-acetylated with deuterated acetic anhydride and then N-acetyl-GlcN-ABEE was prepared. The content of deuterated N-acetyl-GlcN-ABEE was determined to be 50% based on the relative intensity of the acetyl proton signal in the 1D-(1)H NMR spectrum. It was concluded that Rha4N is mostly N-l-lactylated and GlcN is substoichiometrically N-acetylated.

  14. Formation of Stylet Sheaths in āere (in air) from eight species of phytophagous hemipterans from six families (Suborders: Auchenorrhyncha and Sternorrhyncha).

    PubMed

    Morgan, J Kent; Luzio, Gary A; Ammar, El-Desouky; Hunter, Wayne B; Hall, David G; Shatters, Robert G

    2013-01-01

    Stylet sheath formation is a common feature among phytophagous hemipterans. These sheaths are considered essential to promote a successful feeding event. Stylet sheath compositions are largely unknown and their mode of solidification remains to be elucidated. This report demonstrates the formation and solidification of in āere (in air) produced stylet sheaths by six hemipteran families: Diaphorina citri (Psyllidae, Asian citrus psyllid), Aphis nerii (Aphididae, oleander/milkweed aphid), Toxoptera citricida (Aphididae, brown citrus aphid), Aphis gossypii (Aphididae, cotton melon aphid), Bemisia tabaci biotype B (Aleyrodidae, whitefly), Homalodisca vitripennis (Cicadellidae, glassy-winged sharpshooter), Ferrisia virgata (Pseudococcidae, striped mealybug), and Protopulvinaria pyriformis (Coccidae, pyriform scale). Examination of in āere produced stylet sheaths by confocal and scanning electron microscopy shows a common morphology of an initial flange laid down on the surface of the membrane followed by continuous hollow core structures with sequentially stacked hardened bulbous droplets. Single and multi-branched sheaths were common, whereas mealybug and scale insects typically produced multi-branched sheaths. Micrographs of the in āere formed flanges indicate flange sealing upon stylet bundle extraction in D. citri and the aphids, while the B. tabaci whitefly and H. vitripennis glassy-winged sharpshooter flanges remain unsealed. Structural similarity of in āere sheaths are apparent in stylet sheaths formed in planta, in artificial diets, or in water. The use of 'Solvy', a dissolvable membrane, for intact stylet sheath isolation is reported. These observations illustrate for the first time this mode of stylet sheath synthesis adding to the understanding of stylet sheath formation in phytophagous hemipterans and providing tools for future use in structural and compositional analysis.

  15. Formation of Stylet Sheaths in āere (in air) from eight species of phytophagous hemipterans from six families (Suborders: Auchenorrhyncha and Sternorrhyncha).

    PubMed

    Morgan, J Kent; Luzio, Gary A; Ammar, El-Desouky; Hunter, Wayne B; Hall, David G; Shatters, Robert G

    2013-01-01

    Stylet sheath formation is a common feature among phytophagous hemipterans. These sheaths are considered essential to promote a successful feeding event. Stylet sheath compositions are largely unknown and their mode of solidification remains to be elucidated. This report demonstrates the formation and solidification of in āere (in air) produced stylet sheaths by six hemipteran families: Diaphorina citri (Psyllidae, Asian citrus psyllid), Aphis nerii (Aphididae, oleander/milkweed aphid), Toxoptera citricida (Aphididae, brown citrus aphid), Aphis gossypii (Aphididae, cotton melon aphid), Bemisia tabaci biotype B (Aleyrodidae, whitefly), Homalodisca vitripennis (Cicadellidae, glassy-winged sharpshooter), Ferrisia virgata (Pseudococcidae, striped mealybug), and Protopulvinaria pyriformis (Coccidae, pyriform scale). Examination of in āere produced stylet sheaths by confocal and scanning electron microscopy shows a common morphology of an initial flange laid down on the surface of the membrane followed by continuous hollow core structures with sequentially stacked hardened bulbous droplets. Single and multi-branched sheaths were common, whereas mealybug and scale insects typically produced multi-branched sheaths. Micrographs of the in āere formed flanges indicate flange sealing upon stylet bundle extraction in D. citri and the aphids, while the B. tabaci whitefly and H. vitripennis glassy-winged sharpshooter flanges remain unsealed. Structural similarity of in āere sheaths are apparent in stylet sheaths formed in planta, in artificial diets, or in water. The use of 'Solvy', a dissolvable membrane, for intact stylet sheath isolation is reported. These observations illustrate for the first time this mode of stylet sheath synthesis adding to the understanding of stylet sheath formation in phytophagous hemipterans and providing tools for future use in structural and compositional analysis. PMID:23638086

  16. Electron microscope and low-angle x-ray diffraction studies of the nerve myelin sheath.

    PubMed

    FERNANDEZ-MORAN, H; FINEAN, J B

    1957-09-25

    1. A close correlation has been obtained between high resolution electron microscopy and low-angle x-ray diffraction studies of the myelin sheath of frog and rat peripheral and central nerves. Extensive studies were performed by application of both techniques to the same specimens, prepared for examination by OsO(4) or KMnO(4) fixation, and embedding either in methacrylate or in gelatin employing a new procedure. Controlled physical and chemical modifications of the myelin sheath prior to fixation were also investigated. 2. A correspondence was established between the layer spacings observed in electron micrographs and the fundamental radial repeating unit indicated by the low-angle x-ray diffraction patterns. The variations in relative intensities of the low-angle x-ray reflections could be related to the radial density distributions seen in the electron micrographs. 3. An analysis of the preparation procedures revealed that OsO(4) fixation introduces a greater shrinkage of the layer spacings and more pronounced changes in the density distribution within the layers than KMnO(4) fixation. The effects of methacrylate and gelatin embedding are described, and their relative merits considered in relation to the preservation of myelin structure by OsO(4) fixation. 4. The experimental modifications introduced by freezing and thawing of fresh whole nerve are described, particularly the enhancement of the intermediate lines and the dissociation of the layer components in the myelin sheath. A characteristic collapsing of the radial period of the sheath is observed after subjecting fresh nerve trunks to prolonged and intense ultracentrifugation. 5. Controlled extraction of fresh nerve with acetone at 0 degrees C., which preferentially removes cholesterol, produces characteristic, differentiated modifications of the myelin sheath structure. Electron microscopy reveals several types of modifications within a single preparation, including both expanded and collapsed layer

  17. Impact of Plasma Sheath on Rocket-based E-region Ion Measurements

    NASA Astrophysics Data System (ADS)

    Imtiaz, N.; Burchill, J. K.; Marchand, R.

    2013-12-01

    We model the particle velocity distribution functions around the entrance window of the Suprathermal Ion Imager (SII) to assess the impact of electrostatic sheath on ion measurements in the E-region ionosphere. The SII sensor is an electrostatic analyzer that measures two dimensional slices of the distribution of the kinetic energies and arrival-angles of low energy ions. The study is concerned with the interpretation of data obtained from the sensor SII that was affixed to a 1-m NASA rocket 36.234 as part of the Joule II mission to investigate Joule heating in the E-region ionosphere. The rocket flew into quiet auroral conditions above Northern Alaska on 19 January 2007. The payload was spin-stabilitized with a period of 1.6 s, giving an apparent rotation of the ion flow velocity in the frame of reference of the SII. We numerically investigate the ram velocity effect on the ions velocity distributions in the vicinity of SII aperture at an altitudes of approximately 150km. The electrostatic sheath potential profiles surrounding the sensor and payload are calculated numerically with the PIC code PTetra. It is observed that the direction of the ion flow velocity vector modifies the plasma sheath potential profile. This in turn impacts the velocity distributions of molecular oxygen and Nitric oxideions at the aperture of the particle sensor. The velocity distribution functions are calculated by using test-particle modeling. These particle distribution functions are then used to inject the particles in the particle sensor, and to calculate the fluxes on the sensor microchannel plate (MCP).

  18. Modeling and motion compensation of a bidirectional tendon-sheath actuated system for robotic endoscopic surgery.

    PubMed

    Sun, Zhenglong; Wang, Zheng; Phee, Soo Jay

    2015-04-01

    Recent study shows that tendon-sheath system (TSS) has great potential in the development of surgical robots for endoscopic surgery. It is able to deliver adequate power in a light-weight and compact package. And the flexibility and compliance of the tendon-sheath system make it capable of adapting to the long and winding path in the flexible endoscope. However, the main difficulties in precise control of such system fall on the nonlinearities of the system behavior and absence of necessary sensory feedback at the surgical end-effectors. Since accurate position control of the tool is a prerequisite for efficacy, safety and intuitive user-experience in robotic surgery, in this paper we propose a system modeling approach for motion compensation. Based on a bidirectional actuated system using two separate tendon-sheaths, motion transmission is firstly characterized. Two types of positional errors due to system backlash and environment loading are defined and modeled. Then a model-based feedforward compensation method is proposed for open-loop control, giving the system abilities to adjust according to changes in the transmission route configuration without any information feedback from the distal end. A dedicated experimental platform emulating a bidirectional TSS robotic system for endoscopic surgery is built for testing. Proposed positional errors are identified and verified. The performance of the proposed motion compensation is evaluated by trajectory tracking under different environment loading conditions. And the results demonstrate that accurate position control can be achieved even if the transmission route configuration is updated. PMID:25819033

  19. Glyceraldehyde 3-phosphate dehydrogenase is bound to the fibrous sheath of mammalian spermatozoa.

    PubMed

    Westhoff, D; Kamp, G

    1997-08-01

    Evidence is provided that the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase is covalently linked to the fibrous sheath. The fibrous sheath is a typical structure of mammalian spermatozoa surrounding the axoneme in the principal piece of the flagellum. More than 90% of boar sperm glyceraldehyde 3-phosphate dehydrogenase activity is sedimented after cell disintegration by centrifugation. Detergents, different salt concentrations or short term incubation with chymotrypsin do not solubilize the enzyme, whereas digestion with trypsin or elastase does. Short term incubation with trypsin (15 minutes) even resulted in an activation of glyceraldehyde 3-phosphate dehydrogenase. Purification on phenyl-Sepharose yielded a homogeneous glyceraldehyde 3-phosphate dehydrogenase as judged from gel electrophoresis SDS-PAGE and native gradient PAGE. The molecular masses are 41.5 and 238 kDa, respectively, suggesting native glyceraldehyde 3-phosphate dehydrogenase to be a hexamer. Rabbit polyclonal antibodies raised to purified glyceraldehyde 3-phosphate dehydrogenase show a high specificity for mammalian spermatozoal glyceraldehyde 3-phosphate dehydrogenase, while other proteins of boar spermatozoa or the muscle glyceraldehyde 3-phosphate dehydrogenase are not labelled. Immunogold staining performed in a post-embedding procedure reveals the localization of glyceraldehyde 3-phosphate dehydrogenase along the fibrous sheath in spermatozoa of boar, bull, rat, stallion and man. Other structures such as the cell membrane, dense fibres, the axoneme or the mitochondria are free of label. During the process of sperm maturation, most of the cytoplasm of the sperm midpiece is removed as droplets during the passage through the epididymis. The labelling of this cytoplasm, in immature boar spermatozoa and in the droplets, indicates that glyceraldehyde 3-phosphate dehydrogenase is completely removed from the midpiece during sperm maturation in the epididymis. The inverse

  20. Investigation Of The Dust Particles Trapping In Electrostatic Sheaths Of Plasma Discharge

    SciTech Connect

    Tahraoui; Zaham, B.; Annou, R.; Bougdira, J.; Hugon, R.

    2008-09-23

    In this work, a 1D steady state model to study the dynamics along with trapping of dust grains in a plasma sheath over the lower electrode in a plasma reactor, is proposed. Electron and negative ions density distributions are taken Boltzmannian whereas positive ions are described by a cold fluid model. Numerous forces acting on dust grains are taken into account, viz, electric force, gravity force, ion drag force, neutral drag force, etc. It is found that trapping is grain size dependent, and it affects only negatively charged grains. The trapping position is determined and the physical parameters controlling the later are discussed.

  1. Potential of boron neutron capture therapy (BNCT) for malignant peripheral nerve sheath tumors (MPNST).

    PubMed

    Fujimoto, Takuya; Andoh, Tooru; Sudo, Tamotsu; Fujita, Ikuo; Fukase, Naomasa; Takeuchi, Tamotsu; Sonobe, Hiroshi; Inoue, Masayoshi; Hirose, Tkanori; Sakuma, Toshiko; Moritake, Hiroshi; Sugimoto, Tohru; Kawamoto, Teruya; Fukumori, Yoshinobu; Yamamoto, Satomi; Atagi, Shinji; Sakurai, Yoshinori; Kurosaka, Masahiro; Ono, Koji; Ichikawa, Hideki; Suzuki, Minoru

    2015-12-01

    Malignant peripheral nerve sheath tumors (MPNST) are relatively rare neoplasms with poor prognosis. At present there is no effective treatment for MPNST other than surgical resection. Nonetheless, the anti-tumor effect of boron neutron capture therapy (BNCT) was recently demonstrated in two patients with MPNST. Subsequently, tumor-bearing nude mice subcutaneously transplanted with a human MPNST cell line were injected with p-borono-L-phenylalanine (L-BPA) and subjected to BNCT. Pathological studies then revealed that the MPNST cells were selectively destroyed by BNCT.

  2. Measurements of Sheath Currents and Equilibrium Potential on the Explorer VIII Satellite (1960 xi)

    NASA Technical Reports Server (NTRS)

    Bourdeau, R. E.; Donley, J. L.; Serbu, G. P.; Whipple, E. C., Jr.

    1961-01-01

    Experimental data were obtained from the Explorer VIII satellite on five parameters pertinent to the problem of the interaction of space vehicles with an ionized atmosphere. The five parameters are: photoemission current due to electrons emitted from the satellite surfaces as a result of solar radiation; electron and positive ion currents due to the diffusion of charged particles from the medium to the spacecraft; the vehicle potential relative to the medium, and the ambient electron temperature. Included in the experimental data is the aspect dependence of the photoemission and diffusion currents. On the basis of the observations, certain characteristics of the satellite's plasma sheath are postulated.

  3. Control of target-normal-sheath-accelerated protons from a guiding cone

    SciTech Connect

    Zou, D. B.; Zhuo, H. B.; Yang, X. H.; Yu, T. P.; Shao, F. Q.; Pukhov, A.

    2015-06-15

    It is demonstrated through particle-in-cell simulations that target-normal-sheath-accelerated protons can be well controlled by using a guiding cone. Compared to a conventional planar target, both the collimation and number density of proton beams are substantially improved, giving a high-quality proton beam which maintained for a longer distance without degradation. The effect is attributed to the radial electric field resulting from the charge due to the hot target electrons propagating along the cone surface. This electric field can effectively suppress the spatial spread of the protons after the expansion of the hot electrons.

  4. Enhanced Transport Currents in Cu-Sheathed MgB2 Wires

    SciTech Connect

    Eisterer, M; Glowacki, B A.; Weber, H W.; Greenwood, Lawrence R. ); Majoros, M

    2002-01-01

    Copper sheathed MgB2 wires, prepared by an in-situ process, were exposed to neutron radiation in order to introduce defects into the superconductor. The high level of disorder (4.6 x 10{sup -2} dpa) leads to a decreases of the transition temperature by more than 4 K, but to an increase of the slope of the irreversibility line, thus resulting in higher irreversibility fields at low temperatures. The transport currents are significantly enhanced at 4.2 K for fields above 2 T.

  5. Determination of Plasma Sheath and Dust Parameters from Dust Particle Oscillation Modes

    NASA Astrophysics Data System (ADS)

    Qiao, Ke; Carmona-Reyes, Jorge; Smith, Bernard; Cook, Mike; Schmoke, Jimmy; Hyde, Truell

    2007-11-01

    The fundamental parameters of a complex dusty plasma system, including particle charge and dust Debye length, can be determined from the thermally excited oscillation modes of an arbitrary number of dust particles (either a dust cluster or plasma crystal) confined on a 2D plane within the plasma sheath produced above the lower electrode of a GEC reference cell [Ref. 1-2]. This paper will discuss an experimental technique allowing the strength of the confining potential well on the horizontal direction to be determined in the same manner. This technique will be further applied to systems of dust grains comprised of both melamine formaldehyde and ferromagnetic monodisperse particles.

  6. RF-sheath heat flux estimates on Tore Supra and JET ICRF antennae. Extrapolation to ITER

    SciTech Connect

    Colas, L.; Portafaix, C.; Goniche, M.; Jacquet, Ph.

    2009-11-26

    RF-sheath induced heat loads are identified from infrared thermography measurements on Tore Supra ITER-like prototype and JET A2 antennae, and are quantified by fitting thermal calculations. Using a simple scaling law assessed experimentally, the estimated heat fluxes are then extrapolated to the ITER ICRF launcher delivering 20 MW RF power for several plasma scenarios. Parallel heat fluxes up to 6.7 MW/m{sup 2} are expected very locally on ITER antenna front face. The role of edge density on operation is stressed as a trade-off between easy RF coupling and reasonable heat loads. Sources of uncertainty on the results are identified.

  7. Biophysical studies on the structure and function of molecules from the vertebrate myelin sheath

    NASA Astrophysics Data System (ADS)

    Wang, Chaozhan; Myllykoski, Matti; Kursula, Petri

    2010-11-01

    The myelin sheath is a crucial structure for the proper functioning of the vertebrate nervous system. We employ diverse methods to study the structure, function, and dynamics of the molecules specifically present in myelin. Eventually, we hope to better understand the details of the tightly packed myelin structure and the etiology of myelin-related diseases. The paper will provide background into the molecular structure of myelin, and recent results from our laboratory, dealing with the structure and function of selected myelin proteins, will be highlighted.

  8. Calculation of sheath and wake structure about a pillbox-shaped spacecraft in a flowing plasma

    NASA Technical Reports Server (NTRS)

    Parker, L. W.

    1977-01-01

    A computer program was used for studies of the disturbed zones around bodies in flowing plasmas, particularly spacecraft and their associated sheaths and wakes. The program solved a coupled Poisson-Vlasov system of nonlinear partial differential integral equations to obtain distributions of electric potential and ion and electron density about a finite length cylinder in a plasma flow at arbitrary ion Mach numbers. The approach was applicable to a larger range of parameters than other available approaches. In sample calculations, bodies up to 100 Debye lengths in radius were treated, that is, larger than any previously treated realistically. Applications were made to in-situ satellite experiments.

  9. Fast, kinetically self-consistent simulation of RF modulated plasma boundary sheaths

    NASA Astrophysics Data System (ADS)

    Shihab, Mohammed; Ziegler, Dennis; Brinkmann, Ralf Peter

    2012-05-01

    A mathematical model is presented which enables the efficient, kinetically self-consistent simulation of RF modulated plasma boundary sheaths in all technically relevant discharge regimes. It is defined on a one-dimensional geometry where a Cartesian x-axis points from the electrode or wall at xE ≡ 0 towards the plasma bulk. An arbitrary endpoint xB is chosen ‘deep in the bulk’. The model consists of a set of kinetic equations for the ions, Boltzmann's relation for the electrons and Poisson's equation for the electrical field. Boundary conditions specify the ion flux at xB and a periodically—not necessarily harmonically—modulated sheath voltage V(t) or sheath charge Q(t). The equations are solved in a statistical sense. However, it is not the well-known particle-in-cell (PIC) scheme that is employed, but an alternative iterative algorithm termed ensemble-in-spacetime (EST). The basis of the scheme is a discretization of the spacetime, the product of the domain [xE, xB] and the RF period [0, T]. Three modules are called in a sequence. A Monte Carlo module calculates the trajectories of a large set of ions from their start at xB until they reach the electrode at xE, utilizing the potential values on the nodes of the spatio-temporal grid. A harmonic analysis module reconstructs the Fourier modes nim(x) of the ion density ni(x, t) from the calculated trajectories. A field module finally solves the Boltzmann-Poisson equation with the calculated ion densities to generate an updated set of potential values for the spatio-temporal grid. The iteration is started with the potential values of a self-consistent fluid model and terminates when the updates become sufficiently small, i.e. when self-consistency is achieved. A subsequent post-processing determines important quantities, in particular the phase-resolved and phase-averaged values of the ion energy and angular distributions and the total energy flux at the electrode. A drastic reduction of the computational

  10. The polarized Debye sheath effect on Kadomtsev-Petviashvili electrostatic structures in strongly coupled dusty plasma

    SciTech Connect

    Shahmansouri, M.; Alinejad, H.

    2015-04-15

    We give a theoretical investigation on the dynamics of nonlinear electrostatic waves in a strongly coupled dusty plasma with strong electrostatic interaction between dust grains in the presence of the polarization force (i.e., the force due to the polarized Debye sheath). Adopting a reductive perturbation method, we derived a three-dimensional Kadomtsev-Petviashvili equation that describes the evolution of weakly nonlinear electrostatic localized waves. The energy integral equation is used to study the existence domains of the localized structures. The analysis provides the localized structure existence region, in terms of the effects of strong interaction between the dust particles and polarization force.

  11. Preoperative Embolization of a Posterior Mediastinal Lipid-Poor Angiolipoma Mimicking a Paravertebral Nerve Sheath Tumor.

    PubMed

    Gorospe, Luis; García-Poza, Javier; González-Gordaliza, María Cristina; Cabañero-Sánchez, Alberto; Muñoz-Molina, Gemma María; Saldaña-Garrido, David

    2015-08-01

    Mediastinal angiolipomas are extremely rare tumors within the thorax, and only 6 cases have been previously reported in the literature. We describe the case of a lipid-poor angiolipoma within the posterior mediastinum of a 63-year-old man who complained of chest pain. Interestingly, initial imaging of the posterior mediastinal mass of our patient suggested a nerve sheath tumor. A specimen from a percutaneous transthoracic core needle biopsy confirmed an angiolipoma. We decided to preoperatively embolize the posterior mediastinal mass to reduce intraoperative bleeding and to facilitate the excision of the tumor.

  12. Nonlinear surface plasma wave induced target normal sheath acceleration of protons

    SciTech Connect

    Liu, C. S.; Tripathi, V. K. Shao, Xi; Liu, T. C.

    2015-02-15

    The mode structure of a large amplitude surface plasma wave (SPW) over a vacuum–plasma interface, including relativistic and ponderomotive nonlinearities, is deduced. It is shown that the SPW excited by a p-polarized laser on a rippled thin foil target can have larger amplitude than the transmitted laser amplitude and cause stronger target normal sheath acceleration of protons as reported in a recent experiment. Substantial enhancement in proton number also occurs due to the larger surface area covered by the SPW.

  13. Carpal tunnel syndrome caused by a giant cell tumour of the flexor tendon sheath.

    PubMed

    Meek, Marcel F; Sheikh, Zahid A; Quinton, David N

    2014-02-01

    A 76-year-old woman developed right carpal tunnel syndrome after being conservatively treated for tenosynovitis of the flexor tendons with associated mild carpal tunnel syndrome. A magnetic resonance imaging scan showed a tumour in the carpal tunnel. Re-exploration showed that the median nerve was being compressed by a giant cell tumour of the flexor tendon sheaths. Appropriate imaging is advised in patients with additional findings (such as swelling) or in patients with secondary carpal tunnel syndrome and incomplete response to conservative treatment, to exclude a space-occupying lesion.

  14. [Carpal tunnel syndrome and "trigger wrist" revealing a tendinous sheath fibroma].

    PubMed

    Benhima, M A; Ait Essi, F; Abkari, I; Najeb, Y; Fikry, T

    2014-02-01

    The tendinous sheath fibroma (TSF) is a rare benign tumor, exceptionally responsible for carpal tunnel syndrome and "trigger" wrist: we found this association less than ten times in the English and French literature. We report the case of a 63-year-old right-handed carpenter who featured a triggering phenomenon of the right wrist during the flexion-extension movements and compression of the median nerve at the carpal tunnel, secondary to a TSF of the flexor digitorum superficialis. The diagnosis was suspected at the sonography and MRI, the tumor was excised and proven histologically to be a TSF. One year later, the patient remained free of symptoms.

  15. Computed tomography in the evaluation of Brown syndrome of the superior oblique tendon sheath

    SciTech Connect

    Mafee, M.F.; Folk, E.R.; Langer, B.G.; Miller, M.T.; Lagouros, P.; Mittleman, D.

    1985-03-01

    Computed tomographic (CT) findings in 4 patients with superior oblique tendon sheath syndrome (congenital or acquired Brown syndrome) are described. When the inferior oblique muscle moves the eye upward, the superior oblique muscle normally relaxes, while its tendon lengthens and slides freely through the trochlea. In Brown syndrome this process is somehow restricted, which is most apparent during attempts at elevation when the eye is adducted, resulting in an apparent inferior oblique palsy (pseudopalsy). CT is a valuable tool in understanding the pathophysiology and management of acquired Brown syndrome, showing thickening and inflammatory changes of the reflected portion of the superior oblique tendon.

  16. Investigations of the Sheath Effect on the Resultant Magnetic Field of a Cylindrical Monopole Plasma Antenna

    NASA Astrophysics Data System (ADS)

    Moses, E. Emetere

    2015-02-01

    The functionality of the plasma antenna has been narrowed to types and brand names only. The physics of its operation has been neglected and has stagnated technological innovations. The magnetic field in the sheath and plasma were investigated. Notable specifications were worked out in the proposed improved cylindrical monopole plasma antenna. The occurrence of femto spin demagnetization was discovered between the duration of switch on and switch off of the antenna. This phenomenon seems transient because magnetization is highest at the switch on/off point.

  17. Extra-Articular Diffuse Giant Cell Tumor of the Tendon Sheath: A Report of 2 Cases.

    PubMed

    Savvidou, Olga D; Mavrogenis, Andreas F; Sakellariou, Vasilios I; Chloros, George D; Sarlikiotis, Thomas; Papagelopoulos, Panayiotis J

    2016-06-01

    Two rare cases of extra-articular diffuse variant giant cell tumor of the tendon sheath are presented, at the elbow of a 68-year-old female and the foot of a 56-year-old male. Both patients presented with a palpable masses and marginal excision was performed; histological sections confirmed the diagnosis of extra-articular giant cell tumor. No adjuvant therapy was administered. At the latest follow-up, minimum 24 months after excision both patients were disease-free. PMID:27517076

  18. Musculosceletal tuberculosis with involvement of tendon sheaths and formation of synovial cyst.

    PubMed

    Zieliński, Michał; Mazur-Zielińska, Henryka; Kozielski, Jerzy

    2016-01-01

    Due to an increasing amount of patients on immunosuppressive treatment, the number of tuberculosis (TB) of atypical course and extrapulmonary tuberculosis cases increase. Locomotor system is a place of every fifth case of extrapulmonary TB. Because of lack of characteristic symptoms, as well as rare co-occurrence of active lung lesions in radiological imaging, proper diagnosis is hard to establish. We present a case of patient on immunosuppressive therapy due to myositis, in whom we diagnosed musculoskeletal tuberculosis in form of involvement of tendon sheath and formation of synovial cyst. PMID:27672070

  19. Endoscopic Loose Body Removal From Zone 2 Flexor Hallucis Longus Tendon Sheath.

    PubMed

    Lui, Tun Hing

    2016-06-01

    Tenosynovial chondromatosis can occur in the flexor hallucis longus tendon sheath. Complete synovectomy and removal of the loose bodies comprise the treatment of choice. An open procedure requires extensive soft-tissue dissection because the flexor hallucis longus tendon is a deep structure except at the hallux. A tendoscopy approach to synovectomy and removal of loose bodies has the advantage of minimally invasive surgery. This technical note outlines pearls and pitfalls and provides a step-by-step guide to performing this procedure. PMID:27656363

  20. Extra-Articular Diffuse Giant Cell Tumor of the Tendon Sheath: A Report of 2 Cases

    PubMed Central

    Savvidou, Olga D.; Mavrogenis, Andreas F.; Sakellariou, Vasilios I.; Chloros, George D.; Sarlikiotis, Thomas; Papagelopoulos, Panayiotis J.

    2016-01-01

    Two rare cases of extra-articular diffuse variant giant cell tumor of the tendon sheath are presented, at the elbow of a 68-year-old female and the foot of a 56-year-old male. Both patients presented with a palpable masses and marginal excision was performed; histological sections confirmed the diagnosis of extra-articular giant cell tumor. No adjuvant therapy was administered. At the latest follow-up, minimum 24 months after excision both patients were disease-free. PMID:27517076

  1. Controlled growth, characterization and thermodynamic behavior of bismuth–tin nanostructures sheathed in carbon nanotubes

    SciTech Connect

    Jeong, Namjo; Hwang, Kyo Sik; Yang, SeungCheol; Lee, Soon-pung

    2014-03-01

    We report the controlled synthesis of bismuth–tin (Bi–Sn) nanostructures sheathed in graphitic shells that resemble carbon nanotubes (CNTs). Our approach is based on a simple catalytic chemical vapor deposition over a mixture of Bi{sub 2}O{sub 3} and SnO{sub 2} supplied as starting materials. Shape control of the nanostructures strongly relies on the weight ratio of Bi{sub 2}O{sub 3} and SnO{sub 2}. Sheathed nanoparticles and nanorods are formed at SnO{sub 2} to Bi{sub 2}O{sub 3} weight ratios of less than 4:1. They are composed of two separate crystals: rhombohedral Bi and tetragonal Sn{sub 19}Bi crystals. On the other hand, the sheathed nanowires are formed at SnO{sub 2} to Bi{sub 2}O{sub 3} weight ratios above 4:1. The nanowires have only tetragonal Sn{sub 19}Bi structure with a diameter of approximately 100 nm. Elementary analyses support the core/shell heterostructure of the resulting products. A favorable temperature for the Sn-rich Sn{sub 19}Bi nanowires is in the range of 700–800 °C, more specifically around 750 °C. Thermodynamic analysis reveals that the CNTs play a significant role in the protection of the Bi–Sn nanostructures during phase transition by temperature change. This simple and reproducible method may be extended to the fabrication of similar binary or ternary nanostructures. - Highlights: • Controlled growth of Bi–Sn nanostructures sheathed in CNTs relies on MSnO{sub 2}/MBi{sub 2}O{sub 3}. • Growth mechanism is based on catalytic reaction of C{sub 2}H{sub 2} over an oxide mixture. • Nanoparticles and nanorods consist of rhombohedral Bi and tetragonal Sn{sub 19}Bi. • A favorable temperature for the Sn{sub 19}Bi nanowires is in the range of 700–800 °C. • CNT acts as a protective barrier during phase change of the Bi–Sn nanostructures.

  2. Two distinct myosin II populations coordinate ovulatory contraction of the myoepithelial sheath in the Caenorhabditis elegans somatic gonad

    PubMed Central

    Ono, Kanako; Ono, Shoichiro

    2016-01-01

    The myoepithelial sheath in the somatic gonad of the nematode Caenorhabditis elegans has nonstriated contractile actomyosin networks that produce highly coordinated contractility for ovulation of mature oocytes. Two myosin heavy chains are expressed in the myoepithelial sheath, which are also expressed in the body-wall striated muscle. The troponin/tropomyosin system is also present and essential for ovulation. Therefore, although the myoepithelial sheath has smooth muscle–like contractile apparatuses, it has a striated muscle–like regulatory mechanism through troponin/tropomyosin. Here we report that the myoepithelial sheath has a distinct myosin population containing nonmuscle myosin II isoforms, which is regulated by phosphorylation and essential for ovulation. MLC-4, a nonmuscle myosin regulatory light chain, localizes to small punctate structures and does not colocalize with large, needle-like myosin filaments containing MYO-3, a striated-muscle myosin isoform. RNA interference of MLC-4, as well as of its upstream regulators, LET-502 (Rho-associated coiled-coil forming kinase) and MEL-11 (a myosin-binding subunit of myosin phosphatase), impairs ovulation. Expression of a phosphomimetic MLC-4 mutant mimicking a constitutively active state also impairs ovulation. A striated-muscle myosin (UNC-54) appears to provide partially compensatory contractility. Thus the results indicate that the two spatially distinct myosin II populations coordinately regulate ovulatory contraction of the myoepithelial sheath. PMID:26864628

  3. Plasma-Sheath Instability in Hall Thrusters Due to Periodic Modulation of the Energy of Secondary Electrons in Cyclotron Motion

    SciTech Connect

    Sydorenko, D.; Smolyakov, A.; Kaganovich, I.; Raitses, Y.

    2008-04-23

    Particle-in-cell simulation of Hall thruster plasmas reveals a plasma-sheath instability manifesting itself as a rearrangement of the plasma sheath near the thruster channel walls accompanied by a sudden change of many discharge parameters. The instability develops when the sheath current as a function of the sheath voltage is in the negative conductivity regime. The major part of the sheath current is produced by beams of secondary electrons counter-streaming between the walls. The negative conductivity is the result of nonlinear dependence of beam-induced secondary electron emission on the plasma potential. The intensity of such emission is defined by the beam energy. The energy of the beam in crossed axial electric and radial magnetic fields is a quasi-periodical function of the phase of cyclotron rotation, which depends on the radial profile of the potential and the thruster channel width. There is a discrete set of stability intervals determined by the final phase of the cyclotron rotation of secondary electrons. As a result, a small variation of the thruster channel width may result in abrupt changes of plasma parameters if the plasma state jumps from one stability interval to another.

  4. The divergence characteristics of constrained-sheath optics systems for use with 5-eV atomic oxygen sources

    NASA Technical Reports Server (NTRS)

    Anderson, John R.; Wilbur, Paul J.

    1989-01-01

    The potential usefulness of the constrained sheath optics concept as a means of controlling the divergence of low energy, high current density ion beams is examined numerically and experimentally. Numerical results demonstrate that some control of the divergence of typical ion beamlets can be achieved at perveance levels of interest by contouring the surface of the constrained sheath properly. Experimental results demonstrate that a sheath can be constrained by a wire mesh attached to the screen plate of the ion optics system. The numerically predicted beamlet divergence characteristics are shown to depart from those measured experimentally, and additional numerical analysis is used to demonstrate that this departure is probably due to distortions of the sheath caused by the fact that it attempts to conform to the individual wires that make up the sheath constraining mesh. The concept is considered potentially useful in controlling the divergence of ion beamlets in applications where low divergence, low energy, high current density beamlets are being sought, but more work is required to demonstrate this for net beam ion energies as low as 5 eV.

  5. Lymphocyte migration in the micro-channel of splenic sheathed capillaries in Chinese soft-shelled turtles, Pelodiscus sinensis.

    PubMed

    Zhang, Qian; Ullah, Shakeeb; Liu, Yi; Yang, Ping; Chen, Bing; Waqas, Yasir; Bao, Huijun; Hu, Lisi; Li, Quanfu; Chen, Qiusheng

    2016-01-01

    The structural characteristics of the splenic sheathed capillary were investigated using light microscopy and transmission electron microscopy (TEM). This study mainly focused on lymphocyte migration to the splenic white pulp via micro-channels in Chinese soft-shelled turtles, Pelodiscus sinensis. The results showed that the sheathed capillaries in the turtle spleen were high endothelial venule (HEV)-like vessels. These capillaries consist of micro-channels that facilitate lymphocyte migration to the splenic white pulp. The micro-channel is a dynamic structure comprising processes of endothelial cells, supporting cells, and ellipsoid-associated cells (EACs), which provides a microenvironment for lymphocyte migration. The pattern of lymphocyte migration in the micro-channel of the turtle spleen includes the following steps: (i) lymphocyte first adheres to the endothelium of the sheathed capillary, passes through the endothelial cells, and traverses through the basement membrane of the sheathed capillary; (ii) it then enters into the ellipsoid combined with supporting cells and EACs; and (iii) lymphocyte migrates from the ellipsoid to the periellipsoidal lymphatic sheath (PELS) via the micro-channel. This study provides morphological evidence for lymphocyte migration in the micro-channels of turtle spleens and also an insight into the mechanism of lymphocyte homing to the splenic white pulp of reptiles.

  6. The role of antioxidant enzymes in adaptive responses to sheath blight infestation under different fertilization rates and hill densities.

    PubMed

    Wu, Wei; Wan, Xuejie; Shah, Farooq; Fahad, Shah; Huang, Jianliang

    2014-01-01

    Sheath blight of rice, caused by Rhizoctonia solani, is one of the most devastating rice diseases worldwide. No rice cultivar has been found to be completely resistant to this fungus. Identifying antioxidant enzymes activities (activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) and malondialdehyde content (MDA) responding to sheath blight infestation is imperative to understand the defensive mechanism systems of rice. In the present study, two inoculation methods (toothpick and agar block method) were tested in double-season rice. Toothpick method had greater lesion length than agar block method in late season. A higher MDA content was found under toothpick method compared with agar block method, which led to greater POD and SOD activities. Dense planting caused higher lesion length resulting in a higher MDA content, which also subsequently stimulated higher POD and SOD activity. Sheath blight severity was significantly related to the activity of antioxidant enzyme during both seasons. The present study implies that rice plants possess a system of antioxidant protective enzymes which helps them in adaptation to sheath blight infection stresses. Several agronomic practices, such as rational use of fertilizers and optimum planting density, involved in regulating antioxidant protective enzyme systems can be regarded as promising strategy to suppress the sheath blight development.

  7. Most photorespiratory genes are preferentially expressed in the bundle sheath cells of the C4 grass Sorghum bicolor

    PubMed Central

    Döring, Florian; Streubel, Monika; Bräutigam, Andrea; Gowik, Udo

    2016-01-01

    One of the hallmarks of C4 plants is the division of labor between two different photosynthetic cell types, the mesophyll and the bundle sheath cells. C4 plants are of polyphyletic origin and, during the evolution of C4 photosynthesis, the expression of thousands of genes was altered and many genes acquired a cell type-specific or preferential expression pattern. Several lines of evidence, including computational modeling and physiological and phylogenetic analyses, indicate that alterations in the expression of a key photorespiration-related gene, encoding the glycine decarboxylase P subunit, was an early and important step during C4 evolution. Restricting the expression of this gene to the bundle sheath led to the establishment of a photorespiratory CO2 pump. We were interested in whether the expression of genes related to photorespiration remains bundle sheath specific in a fully optimized C4 species. Therefore we analyzed the expression of photorespiratory and C4 cycle genes using RNA in situ hybridization and transcriptome analysis of isolated mesophyll and bundle sheath cells in the C4 grass Sorghum bicolor. It turns out that the C4 metabolism of Sorghum is based solely on the NADP-dependent malic enzyme pathway. The majority of photorespiratory gene expression, with some important exceptions, is restricted to the bundle sheath. PMID:26976818

  8. Surgical removal of infected pacemaker leads without cardiopulmonary bypass after failed extraction using the Excimer Laser Sheath Extraction System.

    PubMed

    Tokunaga, Chiho; Enomoto, Yoshiharu; Sato, Fujio; Kanemoto, Shinya; Matsushita, Shonosuke; Hiramatsu, Yuji; Aonuma, Kazutaka; Sakakibara, Yuzuru

    2012-03-01

    With the growing number of cardiac pacemakers and internal cardioverter defibrillator implantations, problems with endocardial lead infection have been increasing. The newly developed Excimer Laser Sheath Lead Extraction System has been recognized as being highly useful for removing chronic infected leads. However, serious bleeding complications are a concern when this system is used. Here we report our experience with a 67-year-old man who was diagnosed with pacemaker endocarditis. Initially, lead removal was attempted using the Excimer Laser Sheath Extraction System, though this was abandoned because of severe adhesion of the leads and the junction of the supra vena cava (SVC) with the right atrium. Surgical removal of the leads was performed without using cardiopulmonary bypass and the leads were removed without any complications. During surgery, we found there was a silent perforation of the innominate vein brought about by the Excimer Laser Sheath System. Also, the junction of the SVC with the right atrium was thought to be an area potentially at high risk of perforation, because of a lack of surrounding tissue. It is our opinion that those who carry out procedures with the Excimer Laser Sheath System should understand the potential risk of perforation based on cardiac anatomy and should be prepared for lethal bleeding complications. Also, for emergent situations, we believe that close backup by a cardiovascular surgical team should be considered essential for performing the Excimer Laser Sheath Lead Extraction safely.

  9. SHEATHING URANIUM

    DOEpatents

    Colbeck, E.W.

    1959-02-01

    A method is deseribed for forming a conveniently handled corrosion resistant U articlc comprising pouring molten U into an open-ended corrosion resistant metal eontainer such as Cu and its alloys, Al, or austenitic Ni stainless steel. The exposed surface of the cast U is covered with a metallic packing material such as a brazing flux consisting of Al-Si alloy. The container is sealed iii contact with substantially the entire exposed surface of the packing material. The article is then worked mechanically to reduce the cross section. l3651 A thorium--carbon alloy containing 0.1 to 0.5% by weight carbon, whieh is more resistant to water corrosion than pure thorium metal is presented. The alloy is prepared by fusing thorium metal with the desired amount of carbon at a temperature of about 1850 C. It is found that the carbon is present in the alloy as thorium monocarbide

  10. Magnetoplasma sheath waves on a conducting tether in the ionosphere with applications to EMI propagation on large space structures

    NASA Technical Reports Server (NTRS)

    Balmain, K. G.; James, H. G.; Bantin, C. C.

    1991-01-01

    A recent space experiment confirmed sheath-wave propagation of a kilometer-long insulated wire in the ionosphere, oriented parallel to the Earth's magnetic field. This space tether experiment, Oedipus-A, showed a sheath-wave passband up to about 2 MHz and a phase velocity somewhat slower than the velocity of light in a vacuum, and also demonstrated both ease of wave excitation and low attenuation. The evidence suggests that, on any large structure in low Earth orbit, transient or continuous wave electromagnetic interference, once generated, could propagate over the structure via sheath waves, producing unwanted signal levels much higher than in the absence of the ambient plasma medium. Consequently, there is a need for a review of both electromagnetic interference/electromagnetic compatibility standards and ground test procedures as they apply to large structures in low Earth orbit.

  11. Glatiramer acetate, an anti-demyelination drug, reduced rats' epileptic seizures induced by pentylenetetrazol via protection of myelin sheath.

    PubMed

    You, Yu; Zhao, Yaqun; Bai, Hui; Liu, Zhiliang; Meng, Fanxin; Zhang, Hua; Xu, Ruxiang

    2013-06-14

    Glatiramer acetate (GA) is a clinically prescribed immunomodulator drug used to treat demyelinating disease like multiple sclerosis (MS). Persistent down-regulation in the expression of myelin sheath proteins has been observed in both rats with pentylenetetrazol (PTZ) induced chronic epilepsy and some clinical epilepsy patients. Hypothetically, protection of myelin sheath by pharmaceutical means in the process of epilepsy might, to some extent, be helpful to control epileptic seizures. Therefore, we tried to use GA to treat PTZ-induced epilepsy rats. GA treatment successfully protected rats' myelin sheath from demyelination in the process of PTZ-induced epileptic seizures. Notably, electroencephalogram (EEG) monitoring demonstrated that GA-treated epilepsy rats showed significantly lowered epileptiform discharges. Correspondingly, behavioral recording showed reduced frequency of seizures in GA-treated epilepsy rats. The results indicate that epilepsy associated demyelination may be a contributing factor in seizures behavior, and early intervention with anti-demyelination drugs may be beneficial to reduce the severity of seizures behavior.

  12. Examination of ionic wind and cathode sheath effects in a E-field premixed flame with ion density measurements

    NASA Astrophysics Data System (ADS)

    Jacobs, Stewart V.; Xu, Kunning G.

    2016-04-01

    The effect of the ionic wind on a premixed methane-air flame under a DC electric field is studied via mapping of the ion density with Langmuir probes. Ion densities were observed to increase near the burner with increasing electrode voltage up to 6 kV. Past this electrode supply voltage, ion densities ceased increasing and began to decline in some locations within the premixed flame. The increased ion density is caused by an increase in ionic wind force and cathode sheath thickness. The plateau in density is due to the cathode sheath fully encompassing the flame front which is the ion source, thereby collecting all ions in the flame. The spatial density data support the ionic wind hypothesis and provide further explanation of its limits based on the plasma sheath.

  13. Experimental Study of RF Sheath Formation on a Fast Wave Antenna and Limiter in the LAPD

    NASA Astrophysics Data System (ADS)

    Martin, Michael; Gekelman, Walter; Pribyl, Patrick; van Compernolle, Bart; Carter, Troy

    2015-11-01

    Ion cyclotron resonance heating (ICRH) will be an essential component of heating power in ITER. During ICRH, radio frequency (RF) sheaths may form both at the exciting antenna and further away, e.g. in the divertor region, and may cause wall material sputtering and decreased RF power coupling to the plasma. It is important to do detailed laboratory experiments that fully diagnose the sheaths and wave fields. This is not possible in fusion devices. A new RF system has recently been constructed for performing such studies in the LAPD plasma column (ne ~1012 -1013cm-3 , Te ~ 1 - 10 eV ,B0 ~ 400 - 2000 G , diameter ~ 60cm , length ~ 18 m) . The RF system is capable of pulsing at the 1 Hz rep. rate of the LAPD plasma and operating between 2-6 MHz (1st - 9th harmonic of fci in H) with a power output of 200 kW. First results of this system driving a single-strap fast wave antenna will be presented. Emissive and Langmuir probe measurements in the vicinity of both the antenna and a remote limiter and wave coupling measured by magnetic pickup loops will be presented.

  14. A Study of Noncultured Extracted Hair Follicle Outer Root Sheath Cell Suspension for Transplantation in Vitiligo

    PubMed Central

    Shah, Aarti N; Marfatia, Ritu K; Saikia, Siddhartha S

    2016-01-01

    Context: Vitiligo surgeries have come a long way from tissue grafts to cultured and non cultured cell transplantation. Extracted hair follicle outer root sheath cell transplantation (EHF ORS) suspension is more enriched with melanocyte. In a hair bulb, there is one melanocyte for every five keratinocytes which is much higher than the epidermal melanin unit. Aims: To analyse the effectiveness of cultured EHF ORS and to perform objective evaluation based on clinical improvement & photographic evidence. To observe any untoward events or side effects. Settings and Design: The study was open and uncontrolled. All the patients were screened at preliminary visit. Reviews were done every two weeks. The endpoint selected was six months post procedure. Materials and Methods: Twenty five patients of stable Vitiligo were included in the study and follicular unit were harvested by Follicular Unit Extraction method. Outer root sheath cells were extracted by trypsinization. The solution was transplanted over dermabraded recipient site. Pressure dressing was given. Patients were followed up regularly. Statistical Analysis Used: Descriptive Statistics, Chi-Square. Results: Mean ± SD repigmentation was 80.15% ± 22.9% with excellent repigmentation (90-100%) in 60% of patients. Conclusions: This method is safe, effective, and simpler than the other methods involving cell culturing and requiring a laboratory set-up but selection of patients is crucial for the success of the outcome. PMID:27601859

  15. Breast metastases from a malignant peripheral nerve sheath tumor of the kidney: An unusual presentation.

    PubMed

    Koppisetty, Shalini; Alessio, Ricardo C; Rajpurkar, Atul

    2016-01-01

    Malignant peripheral nerve sheath tumors (MPNSTs) are extremely rare soft tissue sarcomas of ectomesenchymal origin. They are commonly seen in association with neurofibromatosis type 1 (NF-1), but can also occur without a history of NF (isolated MPNST). MPNSTs are most commonly located on the extremities (brachial and sacral plexus), head and neck, and trunk regions and are rarely reported in genitourinary organs. These tumors are aggressive, with a high recurrence rate and distant metastases. MPNST involving the kidney is extremely rare, and review of the literature using PubMed from 2001 to 2014 revealed eight cases of MPNST involving the kidney (seven, primarily involving the kidney and one metastatic MPNST of the kidney). Herein, we describe a case of breast metastases from an MPNST of the kidney without a history of NF-1. The patient was initially diagnosed with a spindle cell neoplasm of the kidney with peripheral nerve sheath differentiation. Eventually, the patient developed a right breast mass that was diagnosed as metastatic MPNST. The patient refused any kind of treatment and died 6 months later in hospice care. PMID:27453670

  16. Fibroma of the tendon sheath--a rare hand tumor following repetitive trauma to the palm.

    PubMed

    Yousaf, Muhammad

    2014-01-01

    Fibroma of the tendon sheath (FTS) is a rare, benign, soft tissue lesion. Clinically, FTS presents similarly to the more common giant cell tumour of the tendon sheath. It can be distinguished histologically by the lack of giant cells, foamy histiocytes and synovial cells. The author presents a case of FTS involving the flexor tendon to the fourth metacarpal following repetitive trauma. A 42 year old man presented with a three year history of painless mass in the right palm that had increased in size and became painful recently. Examination demonstrated 6 x 4 cm firm, nodular, superficial mass that was adherent to the underlying structures. Radiographs revealed soft tissue mass. Ultrasound showed a solid heterogeneous mass and the MRI demonstrated that the mass cantered predominantly at the mid and distal portion of fourth metacarpal. Fine Needle Aspiration Cytology was inconclusive. The patient underwent excisional biopsy of the lesion showing lobulated lesion closely resembling hyalinized collagen. Neither vascular proliferations, necrosis, nor mitoses were observed. A diagnosis of FTS was made. The case report provided an additional rare case to literature of a FTS and highlights the need to consider this entity in the differential diagnosis of any soft tissue lesion in the hand after repetitive trauma. Two months later the patient demonstrated full range of movements in the hand. PMID:25603689

  17. Dust particle charge and screening in the collisional RF plasma sheath

    NASA Astrophysics Data System (ADS)

    Beckers, Job; Trienekens, Dirk; Kroesen, Gerrit

    2012-10-01

    Once immersed in plasma, a dust particle gathers a highly negative charge due to the net collection of free electrons. In most plasma's on earth and with particle sizes is in the micrometer range, the gravitational force is dominant and consequently the particle ends up within the plasma sheath region where it is confined due to balancing gravitational and electrical forces. In the plasma sheath region, the Orbital Motion Limited theory predicts charge values that significantly deviate from reality. This is due electron depletion and due the large directed drift velocity of ions, complexifying the prediction of the particle's charge dramatically. We have developed a novel method to measure the charge of a microparticle (10 μm in diameter and confined in a flat potential well above an RF powered electrode) by studying the horizontal interaction with another particle (equally in size) when the angle of the flat part of the potential well is varied with respect to the earth's horizontal plane. Measured particle charges are within the error bars of earlier measurements of the charge of the same particles and comparable plasma conditions during experiments under hyper-gravity conditions in a centrifuge.

  18. The effect of magnetic flux expansion on plasma sheath/presheath

    NASA Astrophysics Data System (ADS)

    Guo, Z. H.; Tang, X. Z.; Berk, H.

    2010-11-01

    Significant magnetic flux expansion can help spread the plasma heat load over a greater area of tokamak divertor plate. It also appears in the expander of an axisymmetric magnetic mirror, which for its favorable magnetic curvature, helps stabilize the global interchange modes in the central cell. For a weakly collisional plasma, the flux expansion introduces a mirror force accelerating the electron and ion flows downstream, which likely induces an ambipolar parallel electric field. This is in addition to the conventional presheath electric field which accelerates the ion to satisfy the Bohm criteria near the wall. We perform kinetic simulations in two spatial and three velocity dimensions to understand (1) the role of mirror force in the parallel and perpendicular thermal energy transfer, and (2) the combined role of mirror-acceleration and parallel electric field on the parallel flow acceleration in the presheath and sheath. The detailed sheath/presheath plasma profiles and the ambipolar electric field will be investigated. Worked supported by OFES.

  19. Spontaneous rectus sheath haematoma in a deceased donor renal transplant recipient: a rare complication.

    PubMed

    Sreenivas, Jayaram; Karthikeyan, Vilvapathy Senguttuvan; SampathKumar, Nathee; Umesha, Lingaraju

    2016-01-01

    Rectus sheath haematoma (RSH) is rarely thought of as a cause of abdominal pain in renal transplant recipients. A 36-year-old woman, a post-deceased donor renal allograft transplant recipient for chronic interstitial nephritis, on triple drug immunosuppression (tacrolimus, mycophenolate mofetil and prednisolone) with basiliximab induction, developed acute vascular rejection and acute tubular injury with suspected antibody-mediated rejection. While on plasmapheresis and haemodialysis for delayed graft function, she developed acute left lower abdominal pain on the 16th postoperative day with tender swelling in the left paraumbilical region. CT of the abdomen showed a large haematoma in the left rectus sheath with no extension. The patient underwent haematoma evacuation through a left paramedian incision and had an uneventful recovery. Serum creatinine stabilised at 0.8 mg/dL and she is on regular follow-up with excellent graft function at 6 months. Diagnosis requires a high index of suspicion, and prompt treatment prevents morbidity and can expedite patient recovery. PMID:26847807

  20. Measurements of plasma sheath heat flux in the Alcator C-Mod divertor

    NASA Astrophysics Data System (ADS)

    Brunner, Dan; Labombard, Brian; Terry, Jim; Reinke, Matt

    2010-11-01

    Heat flux is one of the most important parameters controlling the lifetime of first-wall components in fusion experiments and reactors. The sheath heat flux coefficient (γ) is a parameter relating heat flux (from a plasma to a material surface) to the electron temperature and ion saturation current. Being such a simple expression for a kinetic process, it is of great interest to plasma edge fluid modelers. Under the assumptions of equal ion and electron temperatures, no secondary electron emission, and no net current to the surface the value of γ is approximately 7 [1]. Alcator C-Mod provides a unique opportunity among today's experiments to measure reactor-relevant heat fluxes (100's of MW/m^2 parallel to the magnetic field) in reactor-like divertor geometry. Motivated by the DoE 2010 joint milestone to measure heat flux footprints, the lower outer divertor of Alcator has been instrumented with a suite of Langmuir probes, novel surface thermocouples, and calorimeters in tiles purposefully ramped to eliminate shadowing; all within view of an IR camera. Initial results indicate that the experimentally inferred values of γ are found to agree with simple theory in the sheath limited regime and diverges to lower values as the density increases.